Created starter files for the project.

venv/Lib/site-packages/pip/_internal/vcs/__init__.py

@@ -0,0 +1,15 @@
+# Expose a limited set of classes and functions so callers outside of
+# the vcs package don't need to import deeper than `pip._internal.vcs`.
+# (The test directory and imports protected by MYPY_CHECK_RUNNING may
+# still need to import from a vcs sub-package.)
+# Import all vcs modules to register each VCS in the VcsSupport object.
+import pip._internal.vcs.bazaar
+import pip._internal.vcs.git
+import pip._internal.vcs.mercurial
+import pip._internal.vcs.subversion  # noqa: F401
+from pip._internal.vcs.versioncontrol import (  # noqa: F401
+    RemoteNotFoundError,
+    is_url,
+    make_vcs_requirement_url,
+    vcs,
+)

venv/Lib/site-packages/pip/_internal/vcs/bazaar.py

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+# The following comment should be removed at some point in the future.
+# mypy: disallow-untyped-defs=False
+
+from __future__ import absolute_import
+
+import logging
+import os
+
+from pip._vendor.six.moves.urllib import parse as urllib_parse
+
+from pip._internal.utils.misc import display_path, rmtree
+from pip._internal.utils.subprocess import make_command
+from pip._internal.utils.typing import MYPY_CHECK_RUNNING
+from pip._internal.utils.urls import path_to_url
+from pip._internal.vcs.versioncontrol import VersionControl, vcs
+
+if MYPY_CHECK_RUNNING:
+    from typing import Optional, Tuple
+    from pip._internal.utils.misc import HiddenText
+    from pip._internal.vcs.versioncontrol import AuthInfo, RevOptions
+
+
+logger = logging.getLogger(__name__)
+
+
+class Bazaar(VersionControl):
+    name = 'bzr'
+    dirname = '.bzr'
+    repo_name = 'branch'
+    schemes = (
+        'bzr', 'bzr+http', 'bzr+https', 'bzr+ssh', 'bzr+sftp', 'bzr+ftp',
+        'bzr+lp',
+    )
+
+    def __init__(self, *args, **kwargs):
+        super(Bazaar, self).__init__(*args, **kwargs)
+        # This is only needed for python <2.7.5
+        # Register lp but do not expose as a scheme to support bzr+lp.
+        if getattr(urllib_parse, 'uses_fragment', None):
+            urllib_parse.uses_fragment.extend(['lp'])
+
+    @staticmethod
+    def get_base_rev_args(rev):
+        return ['-r', rev]
+
+    def export(self, location, url):
+        # type: (str, HiddenText) -> None
+        """
+        Export the Bazaar repository at the url to the destination location
+        """
+        # Remove the location to make sure Bazaar can export it correctly
+        if os.path.exists(location):
+            rmtree(location)
+
+        url, rev_options = self.get_url_rev_options(url)
+        self.run_command(
+            make_command('export', location, url, rev_options.to_args())
+        )
+
+    def fetch_new(self, dest, url, rev_options):
+        # type: (str, HiddenText, RevOptions) -> None
+        rev_display = rev_options.to_display()
+        logger.info(
+            'Checking out %s%s to %s',
+            url,
+            rev_display,
+            display_path(dest),
+        )
+        cmd_args = (
+            make_command('branch', '-q', rev_options.to_args(), url, dest)
+        )
+        self.run_command(cmd_args)
+
+    def switch(self, dest, url, rev_options):
+        # type: (str, HiddenText, RevOptions) -> None
+        self.run_command(make_command('switch', url), cwd=dest)
+
+    def update(self, dest, url, rev_options):
+        # type: (str, HiddenText, RevOptions) -> None
+        cmd_args = make_command('pull', '-q', rev_options.to_args())
+        self.run_command(cmd_args, cwd=dest)
+
+    @classmethod
+    def get_url_rev_and_auth(cls, url):
+        # type: (str) -> Tuple[str, Optional[str], AuthInfo]
+        # hotfix the URL scheme after removing bzr+ from bzr+ssh:// readd it
+        url, rev, user_pass = super(Bazaar, cls).get_url_rev_and_auth(url)
+        if url.startswith('ssh://'):
+            url = 'bzr+' + url
+        return url, rev, user_pass
+
+    @classmethod
+    def get_remote_url(cls, location):
+        urls = cls.run_command(['info'], cwd=location)
+        for line in urls.splitlines():
+            line = line.strip()
+            for x in ('checkout of branch: ',
+                      'parent branch: '):
+                if line.startswith(x):
+                    repo = line.split(x)[1]
+                    if cls._is_local_repository(repo):
+                        return path_to_url(repo)
+                    return repo
+        return None
+
+    @classmethod
+    def get_revision(cls, location):
+        revision = cls.run_command(
+            ['revno'], cwd=location,
+        )
+        return revision.splitlines()[-1]
+
+    @classmethod
+    def is_commit_id_equal(cls, dest, name):
+        """Always assume the versions don't match"""
+        return False
+
+
+vcs.register(Bazaar)

venv/Lib/site-packages/pip/_internal/vcs/git.py

@@ -0,0 +1,397 @@
+# The following comment should be removed at some point in the future.
+# mypy: disallow-untyped-defs=False
+
+from __future__ import absolute_import
+
+import logging
+import os.path
+import re
+
+from pip._vendor.packaging.version import parse as parse_version
+from pip._vendor.six.moves.urllib import parse as urllib_parse
+from pip._vendor.six.moves.urllib import request as urllib_request
+
+from pip._internal.exceptions import BadCommand, SubProcessError
+from pip._internal.utils.misc import display_path, hide_url
+from pip._internal.utils.subprocess import make_command
+from pip._internal.utils.temp_dir import TempDirectory
+from pip._internal.utils.typing import MYPY_CHECK_RUNNING
+from pip._internal.vcs.versioncontrol import (
+    RemoteNotFoundError,
+    VersionControl,
+    find_path_to_setup_from_repo_root,
+    vcs,
+)
+
+if MYPY_CHECK_RUNNING:
+    from typing import Optional, Tuple
+    from pip._internal.utils.misc import HiddenText
+    from pip._internal.vcs.versioncontrol import AuthInfo, RevOptions
+
+
+urlsplit = urllib_parse.urlsplit
+urlunsplit = urllib_parse.urlunsplit
+
+
+logger = logging.getLogger(__name__)
+
+
+HASH_REGEX = re.compile('^[a-fA-F0-9]{40}$')
+
+
+def looks_like_hash(sha):
+    return bool(HASH_REGEX.match(sha))
+
+
+class Git(VersionControl):
+    name = 'git'
+    dirname = '.git'
+    repo_name = 'clone'
+    schemes = (
+        'git', 'git+http', 'git+https', 'git+ssh', 'git+git', 'git+file',
+    )
+    # Prevent the user's environment variables from interfering with pip:
+    # https://github.com/pypa/pip/issues/1130
+    unset_environ = ('GIT_DIR', 'GIT_WORK_TREE')
+    default_arg_rev = 'HEAD'
+
+    @staticmethod
+    def get_base_rev_args(rev):
+        return [rev]
+
+    def is_immutable_rev_checkout(self, url, dest):
+        # type: (str, str) -> bool
+        _, rev_options = self.get_url_rev_options(hide_url(url))
+        if not rev_options.rev:
+            return False
+        if not self.is_commit_id_equal(dest, rev_options.rev):
+            # the current commit is different from rev,
+            # which means rev was something else than a commit hash
+            return False
+        # return False in the rare case rev is both a commit hash
+        # and a tag or a branch; we don't want to cache in that case
+        # because that branch/tag could point to something else in the future
+        is_tag_or_branch = bool(
+            self.get_revision_sha(dest, rev_options.rev)[0]
+        )
+        return not is_tag_or_branch
+
+    def get_git_version(self):
+        VERSION_PFX = 'git version '
+        version = self.run_command(['version'])
+        if version.startswith(VERSION_PFX):
+            version = version[len(VERSION_PFX):].split()[0]
+        else:
+            version = ''
+        # get first 3 positions of the git version because
+        # on windows it is x.y.z.windows.t, and this parses as
+        # LegacyVersion which always smaller than a Version.
+        version = '.'.join(version.split('.')[:3])
+        return parse_version(version)
+
+    @classmethod
+    def get_current_branch(cls, location):
+        """
+        Return the current branch, or None if HEAD isn't at a branch
+        (e.g. detached HEAD).
+        """
+        # git-symbolic-ref exits with empty stdout if "HEAD" is a detached
+        # HEAD rather than a symbolic ref.  In addition, the -q causes the
+        # command to exit with status code 1 instead of 128 in this case
+        # and to suppress the message to stderr.
+        args = ['symbolic-ref', '-q', 'HEAD']
+        output = cls.run_command(
+            args, extra_ok_returncodes=(1, ), cwd=location,
+        )
+        ref = output.strip()
+
+        if ref.startswith('refs/heads/'):
+            return ref[len('refs/heads/'):]
+
+        return None
+
+    def export(self, location, url):
+        # type: (str, HiddenText) -> None
+        """Export the Git repository at the url to the destination location"""
+        if not location.endswith('/'):
+            location = location + '/'
+
+        with TempDirectory(kind="export") as temp_dir:
+            self.unpack(temp_dir.path, url=url)
+            self.run_command(
+                ['checkout-index', '-a', '-f', '--prefix', location],
+                cwd=temp_dir.path
+            )
+
+    @classmethod
+    def get_revision_sha(cls, dest, rev):
+        """
+        Return (sha_or_none, is_branch), where sha_or_none is a commit hash
+        if the revision names a remote branch or tag, otherwise None.
+
+        Args:
+          dest: the repository directory.
+          rev: the revision name.
+        """
+        # Pass rev to pre-filter the list.
+
+        output = ''
+        try:
+            output = cls.run_command(['show-ref', rev], cwd=dest)
+        except SubProcessError:
+            pass
+
+        refs = {}
+        for line in output.strip().splitlines():
+            try:
+                sha, ref = line.split()
+            except ValueError:
+                # Include the offending line to simplify troubleshooting if
+                # this error ever occurs.
+                raise ValueError('unexpected show-ref line: {!r}'.format(line))
+
+            refs[ref] = sha
+
+        branch_ref = 'refs/remotes/origin/{}'.format(rev)
+        tag_ref = 'refs/tags/{}'.format(rev)
+
+        sha = refs.get(branch_ref)
+        if sha is not None:
+            return (sha, True)
+
+        sha = refs.get(tag_ref)
+
+        return (sha, False)
+
+    @classmethod
+    def resolve_revision(cls, dest, url, rev_options):
+        # type: (str, HiddenText, RevOptions) -> RevOptions
+        """
+        Resolve a revision to a new RevOptions object with the SHA1 of the
+        branch, tag, or ref if found.
+
+        Args:
+          rev_options: a RevOptions object.
+        """
+        rev = rev_options.arg_rev
+        # The arg_rev property's implementation for Git ensures that the
+        # rev return value is always non-None.
+        assert rev is not None
+
+        sha, is_branch = cls.get_revision_sha(dest, rev)
+
+        if sha is not None:
+            rev_options = rev_options.make_new(sha)
+            rev_options.branch_name = rev if is_branch else None
+
+            return rev_options
+
+        # Do not show a warning for the common case of something that has
+        # the form of a Git commit hash.
+        if not looks_like_hash(rev):
+            logger.warning(
+                "Did not find branch or tag '%s', assuming revision or ref.",
+                rev,
+            )
+
+        if not rev.startswith('refs/'):
+            return rev_options
+
+        # If it looks like a ref, we have to fetch it explicitly.
+        cls.run_command(
+            make_command('fetch', '-q', url, rev_options.to_args()),
+            cwd=dest,
+        )
+        # Change the revision to the SHA of the ref we fetched
+        sha = cls.get_revision(dest, rev='FETCH_HEAD')
+        rev_options = rev_options.make_new(sha)
+
+        return rev_options
+
+    @classmethod
+    def is_commit_id_equal(cls, dest, name):
+        """
+        Return whether the current commit hash equals the given name.
+
+        Args:
+          dest: the repository directory.
+          name: a string name.
+        """
+        if not name:
+            # Then avoid an unnecessary subprocess call.
+            return False
+
+        return cls.get_revision(dest) == name
+
+    def fetch_new(self, dest, url, rev_options):
+        # type: (str, HiddenText, RevOptions) -> None
+        rev_display = rev_options.to_display()
+        logger.info('Cloning %s%s to %s', url, rev_display, display_path(dest))
+        self.run_command(make_command('clone', '-q', url, dest))
+
+        if rev_options.rev:
+            # Then a specific revision was requested.
+            rev_options = self.resolve_revision(dest, url, rev_options)
+            branch_name = getattr(rev_options, 'branch_name', None)
+            if branch_name is None:
+                # Only do a checkout if the current commit id doesn't match
+                # the requested revision.
+                if not self.is_commit_id_equal(dest, rev_options.rev):
+                    cmd_args = make_command(
+                        'checkout', '-q', rev_options.to_args(),
+                    )
+                    self.run_command(cmd_args, cwd=dest)
+            elif self.get_current_branch(dest) != branch_name:
+                # Then a specific branch was requested, and that branch
+                # is not yet checked out.
+                track_branch = 'origin/{}'.format(branch_name)
+                cmd_args = [
+                    'checkout', '-b', branch_name, '--track', track_branch,
+                ]
+                self.run_command(cmd_args, cwd=dest)
+
+        #: repo may contain submodules
+        self.update_submodules(dest)
+
+    def switch(self, dest, url, rev_options):
+        # type: (str, HiddenText, RevOptions) -> None
+        self.run_command(
+            make_command('config', 'remote.origin.url', url),
+            cwd=dest,
+        )
+        cmd_args = make_command('checkout', '-q', rev_options.to_args())
+        self.run_command(cmd_args, cwd=dest)
+
+        self.update_submodules(dest)
+
+    def update(self, dest, url, rev_options):
+        # type: (str, HiddenText, RevOptions) -> None
+        # First fetch changes from the default remote
+        if self.get_git_version() >= parse_version('1.9.0'):
+            # fetch tags in addition to everything else
+            self.run_command(['fetch', '-q', '--tags'], cwd=dest)
+        else:
+            self.run_command(['fetch', '-q'], cwd=dest)
+        # Then reset to wanted revision (maybe even origin/master)
+        rev_options = self.resolve_revision(dest, url, rev_options)
+        cmd_args = make_command('reset', '--hard', '-q', rev_options.to_args())
+        self.run_command(cmd_args, cwd=dest)
+        #: update submodules
+        self.update_submodules(dest)
+
+    @classmethod
+    def get_remote_url(cls, location):
+        """
+        Return URL of the first remote encountered.
+
+        Raises RemoteNotFoundError if the repository does not have a remote
+        url configured.
+        """
+        # We need to pass 1 for extra_ok_returncodes since the command
+        # exits with return code 1 if there are no matching lines.
+        stdout = cls.run_command(
+            ['config', '--get-regexp', r'remote\..*\.url'],
+            extra_ok_returncodes=(1, ), cwd=location,
+        )
+        remotes = stdout.splitlines()
+        try:
+            found_remote = remotes[0]
+        except IndexError:
+            raise RemoteNotFoundError
+
+        for remote in remotes:
+            if remote.startswith('remote.origin.url '):
+                found_remote = remote
+                break
+        url = found_remote.split(' ')[1]
+        return url.strip()
+
+    @classmethod
+    def get_revision(cls, location, rev=None):
+        if rev is None:
+            rev = 'HEAD'
+        current_rev = cls.run_command(
+            ['rev-parse', rev], cwd=location,
+        )
+        return current_rev.strip()
+
+    @classmethod
+    def get_subdirectory(cls, location):
+        """
+        Return the path to setup.py, relative to the repo root.
+        Return None if setup.py is in the repo root.
+        """
+        # find the repo root
+        git_dir = cls.run_command(
+            ['rev-parse', '--git-dir'],
+            cwd=location).strip()
+        if not os.path.isabs(git_dir):
+            git_dir = os.path.join(location, git_dir)
+        repo_root = os.path.abspath(os.path.join(git_dir, '..'))
+        return find_path_to_setup_from_repo_root(location, repo_root)
+
+    @classmethod
+    def get_url_rev_and_auth(cls, url):
+        # type: (str) -> Tuple[str, Optional[str], AuthInfo]
+        """
+        Prefixes stub URLs like 'user@hostname:user/repo.git' with 'ssh://'.
+        That's required because although they use SSH they sometimes don't
+        work with a ssh:// scheme (e.g. GitHub). But we need a scheme for
+        parsing. Hence we remove it again afterwards and return it as a stub.
+        """
+        # Works around an apparent Git bug
+        # (see https://article.gmane.org/gmane.comp.version-control.git/146500)
+        scheme, netloc, path, query, fragment = urlsplit(url)
+        if scheme.endswith('file'):
+            initial_slashes = path[:-len(path.lstrip('/'))]
+            newpath = (
+                initial_slashes +
+                urllib_request.url2pathname(path)
+                .replace('\\', '/').lstrip('/')
+            )
+            url = urlunsplit((scheme, netloc, newpath, query, fragment))
+            after_plus = scheme.find('+') + 1
+            url = scheme[:after_plus] + urlunsplit(
+                (scheme[after_plus:], netloc, newpath, query, fragment),
+            )
+
+        if '://' not in url:
+            assert 'file:' not in url
+            url = url.replace('git+', 'git+ssh://')
+            url, rev, user_pass = super(Git, cls).get_url_rev_and_auth(url)
+            url = url.replace('ssh://', '')
+        else:
+            url, rev, user_pass = super(Git, cls).get_url_rev_and_auth(url)
+
+        return url, rev, user_pass
+
+    @classmethod
+    def update_submodules(cls, location):
+        if not os.path.exists(os.path.join(location, '.gitmodules')):
+            return
+        cls.run_command(
+            ['submodule', 'update', '--init', '--recursive', '-q'],
+            cwd=location,
+        )
+
+    @classmethod
+    def get_repository_root(cls, location):
+        loc = super(Git, cls).get_repository_root(location)
+        if loc:
+            return loc
+        try:
+            r = cls.run_command(
+                ['rev-parse', '--show-toplevel'],
+                cwd=location,
+                log_failed_cmd=False,
+            )
+        except BadCommand:
+            logger.debug("could not determine if %s is under git control "
+                         "because git is not available", location)
+            return None
+        except SubProcessError:
+            return None
+        return os.path.normpath(r.rstrip('\r\n'))
+
+
+vcs.register(Git)

venv/Lib/site-packages/pip/_internal/vcs/mercurial.py

@@ -0,0 +1,158 @@
+# The following comment should be removed at some point in the future.
+# mypy: disallow-untyped-defs=False
+
+from __future__ import absolute_import
+
+import logging
+import os
+
+from pip._vendor.six.moves import configparser
+
+from pip._internal.exceptions import BadCommand, SubProcessError
+from pip._internal.utils.misc import display_path
+from pip._internal.utils.subprocess import make_command
+from pip._internal.utils.temp_dir import TempDirectory
+from pip._internal.utils.typing import MYPY_CHECK_RUNNING
+from pip._internal.utils.urls import path_to_url
+from pip._internal.vcs.versioncontrol import (
+    VersionControl,
+    find_path_to_setup_from_repo_root,
+    vcs,
+)
+
+if MYPY_CHECK_RUNNING:
+    from pip._internal.utils.misc import HiddenText
+    from pip._internal.vcs.versioncontrol import RevOptions
+
+
+logger = logging.getLogger(__name__)
+
+
+class Mercurial(VersionControl):
+    name = 'hg'
+    dirname = '.hg'
+    repo_name = 'clone'
+    schemes = (
+        'hg', 'hg+file', 'hg+http', 'hg+https', 'hg+ssh', 'hg+static-http',
+    )
+
+    @staticmethod
+    def get_base_rev_args(rev):
+        return [rev]
+
+    def export(self, location, url):
+        # type: (str, HiddenText) -> None
+        """Export the Hg repository at the url to the destination location"""
+        with TempDirectory(kind="export") as temp_dir:
+            self.unpack(temp_dir.path, url=url)
+
+            self.run_command(
+                ['archive', location], cwd=temp_dir.path
+            )
+
+    def fetch_new(self, dest, url, rev_options):
+        # type: (str, HiddenText, RevOptions) -> None
+        rev_display = rev_options.to_display()
+        logger.info(
+            'Cloning hg %s%s to %s',
+            url,
+            rev_display,
+            display_path(dest),
+        )
+        self.run_command(make_command('clone', '--noupdate', '-q', url, dest))
+        self.run_command(
+            make_command('update', '-q', rev_options.to_args()),
+            cwd=dest,
+        )
+
+    def switch(self, dest, url, rev_options):
+        # type: (str, HiddenText, RevOptions) -> None
+        repo_config = os.path.join(dest, self.dirname, 'hgrc')
+        config = configparser.RawConfigParser()
+        try:
+            config.read(repo_config)
+            config.set('paths', 'default', url.secret)
+            with open(repo_config, 'w') as config_file:
+                config.write(config_file)
+        except (OSError, configparser.NoSectionError) as exc:
+            logger.warning(
+                'Could not switch Mercurial repository to %s: %s', url, exc,
+            )
+        else:
+            cmd_args = make_command('update', '-q', rev_options.to_args())
+            self.run_command(cmd_args, cwd=dest)
+
+    def update(self, dest, url, rev_options):
+        # type: (str, HiddenText, RevOptions) -> None
+        self.run_command(['pull', '-q'], cwd=dest)
+        cmd_args = make_command('update', '-q', rev_options.to_args())
+        self.run_command(cmd_args, cwd=dest)
+
+    @classmethod
+    def get_remote_url(cls, location):
+        url = cls.run_command(
+            ['showconfig', 'paths.default'],
+            cwd=location).strip()
+        if cls._is_local_repository(url):
+            url = path_to_url(url)
+        return url.strip()
+
+    @classmethod
+    def get_revision(cls, location):
+        """
+        Return the repository-local changeset revision number, as an integer.
+        """
+        current_revision = cls.run_command(
+            ['parents', '--template={rev}'], cwd=location).strip()
+        return current_revision
+
+    @classmethod
+    def get_requirement_revision(cls, location):
+        """
+        Return the changeset identification hash, as a 40-character
+        hexadecimal string
+        """
+        current_rev_hash = cls.run_command(
+            ['parents', '--template={node}'],
+            cwd=location).strip()
+        return current_rev_hash
+
+    @classmethod
+    def is_commit_id_equal(cls, dest, name):
+        """Always assume the versions don't match"""
+        return False
+
+    @classmethod
+    def get_subdirectory(cls, location):
+        """
+        Return the path to setup.py, relative to the repo root.
+        Return None if setup.py is in the repo root.
+        """
+        # find the repo root
+        repo_root = cls.run_command(
+            ['root'], cwd=location).strip()
+        if not os.path.isabs(repo_root):
+            repo_root = os.path.abspath(os.path.join(location, repo_root))
+        return find_path_to_setup_from_repo_root(location, repo_root)
+
+    @classmethod
+    def get_repository_root(cls, location):
+        loc = super(Mercurial, cls).get_repository_root(location)
+        if loc:
+            return loc
+        try:
+            r = cls.run_command(
+                ['root'],
+                cwd=location,
+                log_failed_cmd=False,
+            )
+        except BadCommand:
+            logger.debug("could not determine if %s is under hg control "
+                         "because hg is not available", location)
+            return None
+        except SubProcessError:
+            return None
+        return os.path.normpath(r.rstrip('\r\n'))
+
+
+vcs.register(Mercurial)

venv/Lib/site-packages/pip/_internal/vcs/subversion.py

@@ -0,0 +1,336 @@
+# The following comment should be removed at some point in the future.
+# mypy: disallow-untyped-defs=False
+
+from __future__ import absolute_import
+
+import logging
+import os
+import re
+
+from pip._internal.utils.logging import indent_log
+from pip._internal.utils.misc import (
+    display_path,
+    is_console_interactive,
+    rmtree,
+    split_auth_from_netloc,
+)
+from pip._internal.utils.subprocess import make_command
+from pip._internal.utils.typing import MYPY_CHECK_RUNNING
+from pip._internal.vcs.versioncontrol import VersionControl, vcs
+
+_svn_xml_url_re = re.compile('url="([^"]+)"')
+_svn_rev_re = re.compile(r'committed-rev="(\d+)"')
+_svn_info_xml_rev_re = re.compile(r'\s*revision="(\d+)"')
+_svn_info_xml_url_re = re.compile(r'<url>(.*)</url>')
+
+
+if MYPY_CHECK_RUNNING:
+    from typing import Optional, Tuple
+    from pip._internal.utils.subprocess import CommandArgs
+    from pip._internal.utils.misc import HiddenText
+    from pip._internal.vcs.versioncontrol import AuthInfo, RevOptions
+
+
+logger = logging.getLogger(__name__)
+
+
+class Subversion(VersionControl):
+    name = 'svn'
+    dirname = '.svn'
+    repo_name = 'checkout'
+    schemes = ('svn', 'svn+ssh', 'svn+http', 'svn+https', 'svn+svn')
+
+    @classmethod
+    def should_add_vcs_url_prefix(cls, remote_url):
+        return True
+
+    @staticmethod
+    def get_base_rev_args(rev):
+        return ['-r', rev]
+
+    @classmethod
+    def get_revision(cls, location):
+        """
+        Return the maximum revision for all files under a given location
+        """
+        # Note: taken from setuptools.command.egg_info
+        revision = 0
+
+        for base, dirs, _ in os.walk(location):
+            if cls.dirname not in dirs:
+                dirs[:] = []
+                continue    # no sense walking uncontrolled subdirs
+            dirs.remove(cls.dirname)
+            entries_fn = os.path.join(base, cls.dirname, 'entries')
+            if not os.path.exists(entries_fn):
+                # FIXME: should we warn?
+                continue
+
+            dirurl, localrev = cls._get_svn_url_rev(base)
+
+            if base == location:
+                base = dirurl + '/'   # save the root url
+            elif not dirurl or not dirurl.startswith(base):
+                dirs[:] = []
+                continue    # not part of the same svn tree, skip it
+            revision = max(revision, localrev)
+        return revision
+
+    @classmethod
+    def get_netloc_and_auth(cls, netloc, scheme):
+        """
+        This override allows the auth information to be passed to svn via the
+        --username and --password options instead of via the URL.
+        """
+        if scheme == 'ssh':
+            # The --username and --password options can't be used for
+            # svn+ssh URLs, so keep the auth information in the URL.
+            return super(Subversion, cls).get_netloc_and_auth(netloc, scheme)
+
+        return split_auth_from_netloc(netloc)
+
+    @classmethod
+    def get_url_rev_and_auth(cls, url):
+        # type: (str) -> Tuple[str, Optional[str], AuthInfo]
+        # hotfix the URL scheme after removing svn+ from svn+ssh:// readd it
+        url, rev, user_pass = super(Subversion, cls).get_url_rev_and_auth(url)
+        if url.startswith('ssh://'):
+            url = 'svn+' + url
+        return url, rev, user_pass
+
+    @staticmethod
+    def make_rev_args(username, password):
+        # type: (Optional[str], Optional[HiddenText]) -> CommandArgs
+        extra_args = []  # type: CommandArgs
+        if username:
+            extra_args += ['--username', username]
+        if password:
+            extra_args += ['--password', password]
+
+        return extra_args
+
+    @classmethod
+    def get_remote_url(cls, location):
+        # In cases where the source is in a subdirectory, not alongside
+        # setup.py we have to look up in the location until we find a real
+        # setup.py
+        orig_location = location
+        while not os.path.exists(os.path.join(location, 'setup.py')):
+            last_location = location
+            location = os.path.dirname(location)
+            if location == last_location:
+                # We've traversed up to the root of the filesystem without
+                # finding setup.py
+                logger.warning(
+                    "Could not find setup.py for directory %s (tried all "
+                    "parent directories)",
+                    orig_location,
+                )
+                return None
+
+        return cls._get_svn_url_rev(location)[0]
+
+    @classmethod
+    def _get_svn_url_rev(cls, location):
+        from pip._internal.exceptions import SubProcessError
+
+        entries_path = os.path.join(location, cls.dirname, 'entries')
+        if os.path.exists(entries_path):
+            with open(entries_path) as f:
+                data = f.read()
+        else:  # subversion >= 1.7 does not have the 'entries' file
+            data = ''
+
+        if (data.startswith('8') or
+                data.startswith('9') or
+                data.startswith('10')):
+            data = list(map(str.splitlines, data.split('\n\x0c\n')))
+            del data[0][0]  # get rid of the '8'
+            url = data[0][3]
+            revs = [int(d[9]) for d in data if len(d) > 9 and d[9]] + [0]
+        elif data.startswith('<?xml'):
+            match = _svn_xml_url_re.search(data)
+            if not match:
+                raise ValueError(
+                    'Badly formatted data: {data!r}'.format(**locals()))
+            url = match.group(1)    # get repository URL
+            revs = [int(m.group(1)) for m in _svn_rev_re.finditer(data)] + [0]
+        else:
+            try:
+                # subversion >= 1.7
+                # Note that using get_remote_call_options is not necessary here
+                # because `svn info` is being run against a local directory.
+                # We don't need to worry about making sure interactive mode
+                # is being used to prompt for passwords, because passwords
+                # are only potentially needed for remote server requests.
+                xml = cls.run_command(
+                    ['info', '--xml', location],
+                )
+                url = _svn_info_xml_url_re.search(xml).group(1)
+                revs = [
+                    int(m.group(1)) for m in _svn_info_xml_rev_re.finditer(xml)
+                ]
+            except SubProcessError:
+                url, revs = None, []
+
+        if revs:
+            rev = max(revs)
+        else:
+            rev = 0
+
+        return url, rev
+
+    @classmethod
+    def is_commit_id_equal(cls, dest, name):
+        """Always assume the versions don't match"""
+        return False
+
+    def __init__(self, use_interactive=None):
+        # type: (bool) -> None
+        if use_interactive is None:
+            use_interactive = is_console_interactive()
+        self.use_interactive = use_interactive
+
+        # This member is used to cache the fetched version of the current
+        # ``svn`` client.
+        # Special value definitions:
+        #   None: Not evaluated yet.
+        #   Empty tuple: Could not parse version.
+        self._vcs_version = None  # type: Optional[Tuple[int, ...]]
+
+        super(Subversion, self).__init__()
+
+    def call_vcs_version(self):
+        # type: () -> Tuple[int, ...]
+        """Query the version of the currently installed Subversion client.
+
+        :return: A tuple containing the parts of the version information or
+            ``()`` if the version returned from ``svn`` could not be parsed.
+        :raises: BadCommand: If ``svn`` is not installed.
+        """
+        # Example versions:
+        #   svn, version 1.10.3 (r1842928)
+        #      compiled Feb 25 2019, 14:20:39 on x86_64-apple-darwin17.0.0
+        #   svn, version 1.7.14 (r1542130)
+        #      compiled Mar 28 2018, 08:49:13 on x86_64-pc-linux-gnu
+        #   svn, version 1.12.0-SlikSvn (SlikSvn/1.12.0)
+        #      compiled May 28 2019, 13:44:56 on x86_64-microsoft-windows6.2
+        version_prefix = 'svn, version '
+        version = self.run_command(['--version'])
+
+        if not version.startswith(version_prefix):
+            return ()
+
+        version = version[len(version_prefix):].split()[0]
+        version_list = version.partition('-')[0].split('.')
+        try:
+            parsed_version = tuple(map(int, version_list))
+        except ValueError:
+            return ()
+
+        return parsed_version
+
+    def get_vcs_version(self):
+        # type: () -> Tuple[int, ...]
+        """Return the version of the currently installed Subversion client.
+
+        If the version of the Subversion client has already been queried,
+        a cached value will be used.
+
+        :return: A tuple containing the parts of the version information or
+            ``()`` if the version returned from ``svn`` could not be parsed.
+        :raises: BadCommand: If ``svn`` is not installed.
+        """
+        if self._vcs_version is not None:
+            # Use cached version, if available.
+            # If parsing the version failed previously (empty tuple),
+            # do not attempt to parse it again.
+            return self._vcs_version
+
+        vcs_version = self.call_vcs_version()
+        self._vcs_version = vcs_version
+        return vcs_version
+
+    def get_remote_call_options(self):
+        # type: () -> CommandArgs
+        """Return options to be used on calls to Subversion that contact the server.
+
+        These options are applicable for the following ``svn`` subcommands used
+        in this class.
+
+            - checkout
+            - export
+            - switch
+            - update
+
+        :return: A list of command line arguments to pass to ``svn``.
+        """
+        if not self.use_interactive:
+            # --non-interactive switch is available since Subversion 0.14.4.
+            # Subversion < 1.8 runs in interactive mode by default.
+            return ['--non-interactive']
+
+        svn_version = self.get_vcs_version()
+        # By default, Subversion >= 1.8 runs in non-interactive mode if
+        # stdin is not a TTY. Since that is how pip invokes SVN, in
+        # call_subprocess(), pip must pass --force-interactive to ensure
+        # the user can be prompted for a password, if required.
+        #   SVN added the --force-interactive option in SVN 1.8. Since
+        # e.g. RHEL/CentOS 7, which is supported until 2024, ships with
+        # SVN 1.7, pip should continue to support SVN 1.7. Therefore, pip
+        # can't safely add the option if the SVN version is < 1.8 (or unknown).
+        if svn_version >= (1, 8):
+            return ['--force-interactive']
+
+        return []
+
+    def export(self, location, url):
+        # type: (str, HiddenText) -> None
+        """Export the svn repository at the url to the destination location"""
+        url, rev_options = self.get_url_rev_options(url)
+
+        logger.info('Exporting svn repository %s to %s', url, location)
+        with indent_log():
+            if os.path.exists(location):
+                # Subversion doesn't like to check out over an existing
+                # directory --force fixes this, but was only added in svn 1.5
+                rmtree(location)
+            cmd_args = make_command(
+                'export', self.get_remote_call_options(),
+                rev_options.to_args(), url, location,
+            )
+            self.run_command(cmd_args)
+
+    def fetch_new(self, dest, url, rev_options):
+        # type: (str, HiddenText, RevOptions) -> None
+        rev_display = rev_options.to_display()
+        logger.info(
+            'Checking out %s%s to %s',
+            url,
+            rev_display,
+            display_path(dest),
+        )
+        cmd_args = make_command(
+            'checkout', '-q', self.get_remote_call_options(),
+            rev_options.to_args(), url, dest,
+        )
+        self.run_command(cmd_args)
+
+    def switch(self, dest, url, rev_options):
+        # type: (str, HiddenText, RevOptions) -> None
+        cmd_args = make_command(
+            'switch', self.get_remote_call_options(), rev_options.to_args(),
+            url, dest,
+        )
+        self.run_command(cmd_args)
+
+    def update(self, dest, url, rev_options):
+        # type: (str, HiddenText, RevOptions) -> None
+        cmd_args = make_command(
+            'update', self.get_remote_call_options(), rev_options.to_args(),
+            dest,
+        )
+        self.run_command(cmd_args)
+
+
+vcs.register(Subversion)

venv/Lib/site-packages/pip/_internal/vcs/versioncontrol.py

@@ -0,0 +1,811 @@
+"""Handles all VCS (version control) support"""
+
+from __future__ import absolute_import
+
+import errno
+import logging
+import os
+import shutil
+import subprocess
+import sys
+
+from pip._vendor import pkg_resources
+from pip._vendor.six.moves.urllib import parse as urllib_parse
+
+from pip._internal.exceptions import (
+    BadCommand,
+    InstallationError,
+    SubProcessError,
+)
+from pip._internal.utils.compat import console_to_str, samefile
+from pip._internal.utils.logging import subprocess_logger
+from pip._internal.utils.misc import (
+    ask_path_exists,
+    backup_dir,
+    display_path,
+    hide_url,
+    hide_value,
+    rmtree,
+)
+from pip._internal.utils.subprocess import (
+    format_command_args,
+    make_command,
+    make_subprocess_output_error,
+    reveal_command_args,
+)
+from pip._internal.utils.typing import MYPY_CHECK_RUNNING
+from pip._internal.utils.urls import get_url_scheme
+
+if MYPY_CHECK_RUNNING:
+    from typing import (
+        Dict, Iterable, Iterator, List, Optional, Text, Tuple,
+        Type, Union, Mapping, Any
+    )
+    from pip._internal.utils.misc import HiddenText
+    from pip._internal.utils.subprocess import CommandArgs
+
+    AuthInfo = Tuple[Optional[str], Optional[str]]
+
+
+__all__ = ['vcs']
+
+
+logger = logging.getLogger(__name__)
+
+
+def is_url(name):
+    # type: (Union[str, Text]) -> bool
+    """
+    Return true if the name looks like a URL.
+    """
+    scheme = get_url_scheme(name)
+    if scheme is None:
+        return False
+    return scheme in ['http', 'https', 'file', 'ftp'] + vcs.all_schemes
+
+
+def make_vcs_requirement_url(repo_url, rev, project_name, subdir=None):
+    # type: (str, str, str, Optional[str]) -> str
+    """
+    Return the URL for a VCS requirement.
+
+    Args:
+      repo_url: the remote VCS url, with any needed VCS prefix (e.g. "git+").
+      project_name: the (unescaped) project name.
+    """
+    egg_project_name = pkg_resources.to_filename(project_name)
+    req = '{}@{}#egg={}'.format(repo_url, rev, egg_project_name)
+    if subdir:
+        req += '&subdirectory={}'.format(subdir)
+
+    return req
+
+
+def call_subprocess(
+    cmd,  # type: Union[List[str], CommandArgs]
+    cwd=None,  # type: Optional[str]
+    extra_environ=None,  # type: Optional[Mapping[str, Any]]
+    extra_ok_returncodes=None,  # type: Optional[Iterable[int]]
+    log_failed_cmd=True  # type: Optional[bool]
+):
+    # type: (...) -> Text
+    """
+    Args:
+      extra_ok_returncodes: an iterable of integer return codes that are
+        acceptable, in addition to 0. Defaults to None, which means [].
+      log_failed_cmd: if false, failed commands are not logged,
+        only raised.
+    """
+    if extra_ok_returncodes is None:
+        extra_ok_returncodes = []
+
+    # log the subprocess output at DEBUG level.
+    log_subprocess = subprocess_logger.debug
+
+    env = os.environ.copy()
+    if extra_environ:
+        env.update(extra_environ)
+
+    # Whether the subprocess will be visible in the console.
+    showing_subprocess = True
+
+    command_desc = format_command_args(cmd)
+    try:
+        proc = subprocess.Popen(
+            # Convert HiddenText objects to the underlying str.
+            reveal_command_args(cmd),
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+            cwd=cwd
+        )
+        if proc.stdin:
+            proc.stdin.close()
+    except Exception as exc:
+        if log_failed_cmd:
+            subprocess_logger.critical(
+                "Error %s while executing command %s", exc, command_desc,
+            )
+        raise
+    all_output = []
+    while True:
+        # The "line" value is a unicode string in Python 2.
+        line = None
+        if proc.stdout:
+            line = console_to_str(proc.stdout.readline())
+        if not line:
+            break
+        line = line.rstrip()
+        all_output.append(line + '\n')
+
+        # Show the line immediately.
+        log_subprocess(line)
+    try:
+        proc.wait()
+    finally:
+        if proc.stdout:
+            proc.stdout.close()
+
+    proc_had_error = (
+        proc.returncode and proc.returncode not in extra_ok_returncodes
+    )
+    if proc_had_error:
+        if not showing_subprocess and log_failed_cmd:
+            # Then the subprocess streams haven't been logged to the
+            # console yet.
+            msg = make_subprocess_output_error(
+                cmd_args=cmd,
+                cwd=cwd,
+                lines=all_output,
+                exit_status=proc.returncode,
+            )
+            subprocess_logger.error(msg)
+        exc_msg = (
+            'Command errored out with exit status {}: {} '
+            'Check the logs for full command output.'
+        ).format(proc.returncode, command_desc)
+        raise SubProcessError(exc_msg)
+    return ''.join(all_output)
+
+
+def find_path_to_setup_from_repo_root(location, repo_root):
+    # type: (str, str) -> Optional[str]
+    """
+    Find the path to `setup.py` by searching up the filesystem from `location`.
+    Return the path to `setup.py` relative to `repo_root`.
+    Return None if `setup.py` is in `repo_root` or cannot be found.
+    """
+    # find setup.py
+    orig_location = location
+    while not os.path.exists(os.path.join(location, 'setup.py')):
+        last_location = location
+        location = os.path.dirname(location)
+        if location == last_location:
+            # We've traversed up to the root of the filesystem without
+            # finding setup.py
+            logger.warning(
+                "Could not find setup.py for directory %s (tried all "
+                "parent directories)",
+                orig_location,
+            )
+            return None
+
+    if samefile(repo_root, location):
+        return None
+
+    return os.path.relpath(location, repo_root)
+
+
+class RemoteNotFoundError(Exception):
+    pass
+
+
+class RevOptions(object):
+
+    """
+    Encapsulates a VCS-specific revision to install, along with any VCS
+    install options.
+
+    Instances of this class should be treated as if immutable.
+    """
+
+    def __init__(
+        self,
+        vc_class,  # type: Type[VersionControl]
+        rev=None,  # type: Optional[str]
+        extra_args=None,  # type: Optional[CommandArgs]
+    ):
+        # type: (...) -> None
+        """
+        Args:
+          vc_class: a VersionControl subclass.
+          rev: the name of the revision to install.
+          extra_args: a list of extra options.
+        """
+        if extra_args is None:
+            extra_args = []
+
+        self.extra_args = extra_args
+        self.rev = rev
+        self.vc_class = vc_class
+        self.branch_name = None  # type: Optional[str]
+
+    def __repr__(self):
+        # type: () -> str
+        return '<RevOptions {}: rev={!r}>'.format(self.vc_class.name, self.rev)
+
+    @property
+    def arg_rev(self):
+        # type: () -> Optional[str]
+        if self.rev is None:
+            return self.vc_class.default_arg_rev
+
+        return self.rev
+
+    def to_args(self):
+        # type: () -> CommandArgs
+        """
+        Return the VCS-specific command arguments.
+        """
+        args = []  # type: CommandArgs
+        rev = self.arg_rev
+        if rev is not None:
+            args += self.vc_class.get_base_rev_args(rev)
+        args += self.extra_args
+
+        return args
+
+    def to_display(self):
+        # type: () -> str
+        if not self.rev:
+            return ''
+
+        return ' (to revision {})'.format(self.rev)
+
+    def make_new(self, rev):
+        # type: (str) -> RevOptions
+        """
+        Make a copy of the current instance, but with a new rev.
+
+        Args:
+          rev: the name of the revision for the new object.
+        """
+        return self.vc_class.make_rev_options(rev, extra_args=self.extra_args)
+
+
+class VcsSupport(object):
+    _registry = {}  # type: Dict[str, VersionControl]
+    schemes = ['ssh', 'git', 'hg', 'bzr', 'sftp', 'svn']
+
+    def __init__(self):
+        # type: () -> None
+        # Register more schemes with urlparse for various version control
+        # systems
+        urllib_parse.uses_netloc.extend(self.schemes)
+        # Python >= 2.7.4, 3.3 doesn't have uses_fragment
+        if getattr(urllib_parse, 'uses_fragment', None):
+            urllib_parse.uses_fragment.extend(self.schemes)
+        super(VcsSupport, self).__init__()
+
+    def __iter__(self):
+        # type: () -> Iterator[str]
+        return self._registry.__iter__()
+
+    @property
+    def backends(self):
+        # type: () -> List[VersionControl]
+        return list(self._registry.values())
+
+    @property
+    def dirnames(self):
+        # type: () -> List[str]
+        return [backend.dirname for backend in self.backends]
+
+    @property
+    def all_schemes(self):
+        # type: () -> List[str]
+        schemes = []  # type: List[str]
+        for backend in self.backends:
+            schemes.extend(backend.schemes)
+        return schemes
+
+    def register(self, cls):
+        # type: (Type[VersionControl]) -> None
+        if not hasattr(cls, 'name'):
+            logger.warning('Cannot register VCS %s', cls.__name__)
+            return
+        if cls.name not in self._registry:
+            self._registry[cls.name] = cls()
+            logger.debug('Registered VCS backend: %s', cls.name)
+
+    def unregister(self, name):
+        # type: (str) -> None
+        if name in self._registry:
+            del self._registry[name]
+
+    def get_backend_for_dir(self, location):
+        # type: (str) -> Optional[VersionControl]
+        """
+        Return a VersionControl object if a repository of that type is found
+        at the given directory.
+        """
+        vcs_backends = {}
+        for vcs_backend in self._registry.values():
+            repo_path = vcs_backend.get_repository_root(location)
+            if not repo_path:
+                continue
+            logger.debug('Determine that %s uses VCS: %s',
+                         location, vcs_backend.name)
+            vcs_backends[repo_path] = vcs_backend
+
+        if not vcs_backends:
+            return None
+
+        # Choose the VCS in the inner-most directory. Since all repository
+        # roots found here would be either `location` or one of its
+        # parents, the longest path should have the most path components,
+        # i.e. the backend representing the inner-most repository.
+        inner_most_repo_path = max(vcs_backends, key=len)
+        return vcs_backends[inner_most_repo_path]
+
+    def get_backend_for_scheme(self, scheme):
+        # type: (str) -> Optional[VersionControl]
+        """
+        Return a VersionControl object or None.
+        """
+        for vcs_backend in self._registry.values():
+            if scheme in vcs_backend.schemes:
+                return vcs_backend
+        return None
+
+    def get_backend(self, name):
+        # type: (str) -> Optional[VersionControl]
+        """
+        Return a VersionControl object or None.
+        """
+        name = name.lower()
+        return self._registry.get(name)
+
+
+vcs = VcsSupport()
+
+
+class VersionControl(object):
+    name = ''
+    dirname = ''
+    repo_name = ''
+    # List of supported schemes for this Version Control
+    schemes = ()  # type: Tuple[str, ...]
+    # Iterable of environment variable names to pass to call_subprocess().
+    unset_environ = ()  # type: Tuple[str, ...]
+    default_arg_rev = None  # type: Optional[str]
+
+    @classmethod
+    def should_add_vcs_url_prefix(cls, remote_url):
+        # type: (str) -> bool
+        """
+        Return whether the vcs prefix (e.g. "git+") should be added to a
+        repository's remote url when used in a requirement.
+        """
+        return not remote_url.lower().startswith('{}:'.format(cls.name))
+
+    @classmethod
+    def get_subdirectory(cls, location):
+        # type: (str) -> Optional[str]
+        """
+        Return the path to setup.py, relative to the repo root.
+        Return None if setup.py is in the repo root.
+        """
+        return None
+
+    @classmethod
+    def get_requirement_revision(cls, repo_dir):
+        # type: (str) -> str
+        """
+        Return the revision string that should be used in a requirement.
+        """
+        return cls.get_revision(repo_dir)
+
+    @classmethod
+    def get_src_requirement(cls, repo_dir, project_name):
+        # type: (str, str) -> Optional[str]
+        """
+        Return the requirement string to use to redownload the files
+        currently at the given repository directory.
+
+        Args:
+          project_name: the (unescaped) project name.
+
+        The return value has a form similar to the following:
+
+            {repository_url}@{revision}#egg={project_name}
+        """
+        repo_url = cls.get_remote_url(repo_dir)
+        if repo_url is None:
+            return None
+
+        if cls.should_add_vcs_url_prefix(repo_url):
+            repo_url = '{}+{}'.format(cls.name, repo_url)
+
+        revision = cls.get_requirement_revision(repo_dir)
+        subdir = cls.get_subdirectory(repo_dir)
+        req = make_vcs_requirement_url(repo_url, revision, project_name,
+                                       subdir=subdir)
+
+        return req
+
+    @staticmethod
+    def get_base_rev_args(rev):
+        # type: (str) -> List[str]
+        """
+        Return the base revision arguments for a vcs command.
+
+        Args:
+          rev: the name of a revision to install.  Cannot be None.
+        """
+        raise NotImplementedError
+
+    def is_immutable_rev_checkout(self, url, dest):
+        # type: (str, str) -> bool
+        """
+        Return true if the commit hash checked out at dest matches
+        the revision in url.
+
+        Always return False, if the VCS does not support immutable commit
+        hashes.
+
+        This method does not check if there are local uncommitted changes
+        in dest after checkout, as pip currently has no use case for that.
+        """
+        return False
+
+    @classmethod
+    def make_rev_options(cls, rev=None, extra_args=None):
+        # type: (Optional[str], Optional[CommandArgs]) -> RevOptions
+        """
+        Return a RevOptions object.
+
+        Args:
+          rev: the name of a revision to install.
+          extra_args: a list of extra options.
+        """
+        return RevOptions(cls, rev, extra_args=extra_args)
+
+    @classmethod
+    def _is_local_repository(cls, repo):
+        # type: (str) -> bool
+        """
+           posix absolute paths start with os.path.sep,
+           win32 ones start with drive (like c:\\folder)
+        """
+        drive, tail = os.path.splitdrive(repo)
+        return repo.startswith(os.path.sep) or bool(drive)
+
+    def export(self, location, url):
+        # type: (str, HiddenText) -> None
+        """
+        Export the repository at the url to the destination location
+        i.e. only download the files, without vcs informations
+
+        :param url: the repository URL starting with a vcs prefix.
+        """
+        raise NotImplementedError
+
+    @classmethod
+    def get_netloc_and_auth(cls, netloc, scheme):
+        # type: (str, str) -> Tuple[str, Tuple[Optional[str], Optional[str]]]
+        """
+        Parse the repository URL's netloc, and return the new netloc to use
+        along with auth information.
+
+        Args:
+          netloc: the original repository URL netloc.
+          scheme: the repository URL's scheme without the vcs prefix.
+
+        This is mainly for the Subversion class to override, so that auth
+        information can be provided via the --username and --password options
+        instead of through the URL.  For other subclasses like Git without
+        such an option, auth information must stay in the URL.
+
+        Returns: (netloc, (username, password)).
+        """
+        return netloc, (None, None)
+
+    @classmethod
+    def get_url_rev_and_auth(cls, url):
+        # type: (str) -> Tuple[str, Optional[str], AuthInfo]
+        """
+        Parse the repository URL to use, and return the URL, revision,
+        and auth info to use.
+
+        Returns: (url, rev, (username, password)).
+        """
+        scheme, netloc, path, query, frag = urllib_parse.urlsplit(url)
+        if '+' not in scheme:
+            raise ValueError(
+                "Sorry, {!r} is a malformed VCS url. "
+                "The format is <vcs>+<protocol>://<url>, "
+                "e.g. svn+http://myrepo/svn/MyApp#egg=MyApp".format(url)
+            )
+        # Remove the vcs prefix.
+        scheme = scheme.split('+', 1)[1]
+        netloc, user_pass = cls.get_netloc_and_auth(netloc, scheme)
+        rev = None
+        if '@' in path:
+            path, rev = path.rsplit('@', 1)
+            if not rev:
+                raise InstallationError(
+                    "The URL {!r} has an empty revision (after @) "
+                    "which is not supported. Include a revision after @ "
+                    "or remove @ from the URL.".format(url)
+                )
+        url = urllib_parse.urlunsplit((scheme, netloc, path, query, ''))
+        return url, rev, user_pass
+
+    @staticmethod
+    def make_rev_args(username, password):
+        # type: (Optional[str], Optional[HiddenText]) -> CommandArgs
+        """
+        Return the RevOptions "extra arguments" to use in obtain().
+        """
+        return []
+
+    def get_url_rev_options(self, url):
+        # type: (HiddenText) -> Tuple[HiddenText, RevOptions]
+        """
+        Return the URL and RevOptions object to use in obtain() and in
+        some cases export(), as a tuple (url, rev_options).
+        """
+        secret_url, rev, user_pass = self.get_url_rev_and_auth(url.secret)
+        username, secret_password = user_pass
+        password = None  # type: Optional[HiddenText]
+        if secret_password is not None:
+            password = hide_value(secret_password)
+        extra_args = self.make_rev_args(username, password)
+        rev_options = self.make_rev_options(rev, extra_args=extra_args)
+
+        return hide_url(secret_url), rev_options
+
+    @staticmethod
+    def normalize_url(url):
+        # type: (str) -> str
+        """
+        Normalize a URL for comparison by unquoting it and removing any
+        trailing slash.
+        """
+        return urllib_parse.unquote(url).rstrip('/')
+
+    @classmethod
+    def compare_urls(cls, url1, url2):
+        # type: (str, str) -> bool
+        """
+        Compare two repo URLs for identity, ignoring incidental differences.
+        """
+        return (cls.normalize_url(url1) == cls.normalize_url(url2))
+
+    def fetch_new(self, dest, url, rev_options):
+        # type: (str, HiddenText, RevOptions) -> None
+        """
+        Fetch a revision from a repository, in the case that this is the
+        first fetch from the repository.
+
+        Args:
+          dest: the directory to fetch the repository to.
+          rev_options: a RevOptions object.
+        """
+        raise NotImplementedError
+
+    def switch(self, dest, url, rev_options):
+        # type: (str, HiddenText, RevOptions) -> None
+        """
+        Switch the repo at ``dest`` to point to ``URL``.
+
+        Args:
+          rev_options: a RevOptions object.
+        """
+        raise NotImplementedError
+
+    def update(self, dest, url, rev_options):
+        # type: (str, HiddenText, RevOptions) -> None
+        """
+        Update an already-existing repo to the given ``rev_options``.
+
+        Args:
+          rev_options: a RevOptions object.
+        """
+        raise NotImplementedError
+
+    @classmethod
+    def is_commit_id_equal(cls, dest, name):
+        # type: (str, Optional[str]) -> bool
+        """
+        Return whether the id of the current commit equals the given name.
+
+        Args:
+          dest: the repository directory.
+          name: a string name.
+        """
+        raise NotImplementedError
+
+    def obtain(self, dest, url):
+        # type: (str, HiddenText) -> None
+        """
+        Install or update in editable mode the package represented by this
+        VersionControl object.
+
+        :param dest: the repository directory in which to install or update.
+        :param url: the repository URL starting with a vcs prefix.
+        """
+        url, rev_options = self.get_url_rev_options(url)
+
+        if not os.path.exists(dest):
+            self.fetch_new(dest, url, rev_options)
+            return
+
+        rev_display = rev_options.to_display()
+        if self.is_repository_directory(dest):
+            existing_url = self.get_remote_url(dest)
+            if self.compare_urls(existing_url, url.secret):
+                logger.debug(
+                    '%s in %s exists, and has correct URL (%s)',
+                    self.repo_name.title(),
+                    display_path(dest),
+                    url,
+                )
+                if not self.is_commit_id_equal(dest, rev_options.rev):
+                    logger.info(
+                        'Updating %s %s%s',
+                        display_path(dest),
+                        self.repo_name,
+                        rev_display,
+                    )
+                    self.update(dest, url, rev_options)
+                else:
+                    logger.info('Skipping because already up-to-date.')
+                return
+
+            logger.warning(
+                '%s %s in %s exists with URL %s',
+                self.name,
+                self.repo_name,
+                display_path(dest),
+                existing_url,
+            )
+            prompt = ('(s)witch, (i)gnore, (w)ipe, (b)ackup ',
+                      ('s', 'i', 'w', 'b'))
+        else:
+            logger.warning(
+                'Directory %s already exists, and is not a %s %s.',
+                dest,
+                self.name,
+                self.repo_name,
+            )
+            # https://github.com/python/mypy/issues/1174
+            prompt = ('(i)gnore, (w)ipe, (b)ackup ',  # type: ignore
+                      ('i', 'w', 'b'))
+
+        logger.warning(
+            'The plan is to install the %s repository %s',
+            self.name,
+            url,
+        )
+        response = ask_path_exists('What to do?  {}'.format(
+            prompt[0]), prompt[1])
+
+        if response == 'a':
+            sys.exit(-1)
+
+        if response == 'w':
+            logger.warning('Deleting %s', display_path(dest))
+            rmtree(dest)
+            self.fetch_new(dest, url, rev_options)
+            return
+
+        if response == 'b':
+            dest_dir = backup_dir(dest)
+            logger.warning(
+                'Backing up %s to %s', display_path(dest), dest_dir,
+            )
+            shutil.move(dest, dest_dir)
+            self.fetch_new(dest, url, rev_options)
+            return
+
+        # Do nothing if the response is "i".
+        if response == 's':
+            logger.info(
+                'Switching %s %s to %s%s',
+                self.repo_name,
+                display_path(dest),
+                url,
+                rev_display,
+            )
+            self.switch(dest, url, rev_options)
+
+    def unpack(self, location, url):
+        # type: (str, HiddenText) -> None
+        """
+        Clean up current location and download the url repository
+        (and vcs infos) into location
+
+        :param url: the repository URL starting with a vcs prefix.
+        """
+        if os.path.exists(location):
+            rmtree(location)
+        self.obtain(location, url=url)
+
+    @classmethod
+    def get_remote_url(cls, location):
+        # type: (str) -> str
+        """
+        Return the url used at location
+
+        Raises RemoteNotFoundError if the repository does not have a remote
+        url configured.
+        """
+        raise NotImplementedError
+
+    @classmethod
+    def get_revision(cls, location):
+        # type: (str) -> str
+        """
+        Return the current commit id of the files at the given location.
+        """
+        raise NotImplementedError
+
+    @classmethod
+    def run_command(
+        cls,
+        cmd,  # type: Union[List[str], CommandArgs]
+        cwd=None,  # type: Optional[str]
+        extra_environ=None,  # type: Optional[Mapping[str, Any]]
+        extra_ok_returncodes=None,  # type: Optional[Iterable[int]]
+        log_failed_cmd=True  # type: bool
+    ):
+        # type: (...) -> Text
+        """
+        Run a VCS subcommand
+        This is simply a wrapper around call_subprocess that adds the VCS
+        command name, and checks that the VCS is available
+        """
+        cmd = make_command(cls.name, *cmd)
+        try:
+            return call_subprocess(cmd, cwd,
+                                   extra_environ=extra_environ,
+                                   extra_ok_returncodes=extra_ok_returncodes,
+                                   log_failed_cmd=log_failed_cmd)
+        except OSError as e:
+            # errno.ENOENT = no such file or directory
+            # In other words, the VCS executable isn't available
+            if e.errno == errno.ENOENT:
+                raise BadCommand(
+                    'Cannot find command {cls.name!r} - do you have '
+                    '{cls.name!r} installed and in your '
+                    'PATH?'.format(**locals()))
+            else:
+                raise  # re-raise exception if a different error occurred
+
+    @classmethod
+    def is_repository_directory(cls, path):
+        # type: (str) -> bool
+        """
+        Return whether a directory path is a repository directory.
+        """
+        logger.debug('Checking in %s for %s (%s)...',
+                     path, cls.dirname, cls.name)
+        return os.path.exists(os.path.join(path, cls.dirname))
+
+    @classmethod
+    def get_repository_root(cls, location):
+        # type: (str) -> Optional[str]
+        """
+        Return the "root" (top-level) directory controlled by the vcs,
+        or `None` if the directory is not in any.
+
+        It is meant to be overridden to implement smarter detection
+        mechanisms for specific vcs.
+
+        This can do more than is_repository_directory() alone. For
+        example, the Git override checks that Git is actually available.
+        """
+        if cls.is_repository_directory(location):
+            return location
+        return None