Change check_version() to accept a commit hash / id.

src/pip/_internal/vcs/__init__.py

@@ -279,7 +279,7 @@ class VersionControl(object):
         """
         raise NotImplementedError
 
-    def check_version(self, dest, rev_options):
+    def check_version(self, dest, commit_id):
         """
         Return True if the version is identical to what exists and
         doesn't need to be updated.
@@ -313,7 +313,8 @@ class VersionControl(object):
                         display_path(dest),
                         url,
                     )
-                    if not self.check_version(dest, rev_options):
+                    commit_id = rev_options[0]
+                    if not self.check_version(dest, commit_id):
                         logger.info(
                             'Updating %s %s%s',
                             display_path(dest),

src/pip/_internal/vcs/bazaar.py

@@ -104,7 +104,7 @@ class Bazaar(VersionControl):
         current_rev = self.get_revision(location)
         return '%s@%s#egg=%s' % (repo, current_rev, egg_project_name)
 
-    def check_version(self, dest, rev_options):
+    def check_version(self, dest, commit_id):
         """Always assume the versions don't match"""
         return False
 

src/pip/_internal/vcs/git.py

@@ -119,7 +119,7 @@ class Git(VersionControl):
 
         return rev_options
 
-    def check_version(self, dest, rev_options):
+    def check_version(self, dest, commit_id):
         """
         Compare the current sha to the ref. ref may be a branch or tag name,
         but current rev will always point to a sha. This means that a branch
@@ -129,7 +129,7 @@ class Git(VersionControl):
         Args:
           rev_options: a RevOptions object.
         """
-        return self.get_revision(dest) == rev_options.arg_rev
+        return self.get_revision(dest) == commit_id
 
     def switch(self, dest, url, rev_options):
         self.run_command(['config', 'remote.origin.url', url], cwd=dest)
@@ -164,10 +164,11 @@ class Git(VersionControl):
 
             if rev:
                 rev_options = self.check_rev_options(dest, rev_options)
-                # Only do a checkout if rev_options differs from HEAD
-                if not self.check_version(dest, rev_options):
+                commit_hash = rev_options.rev
+                # Only do a checkout if HEAD differs from commit_hash.
+                if not self.check_version(dest, commit_hash):
                     cmd_args = ['fetch', '-q', url] + rev_options.to_args()
-                    self.run_command(cmd_args, cwd=dest,)
+                    self.run_command(cmd_args, cwd=dest)
                     self.run_command(
                         ['checkout', '-q', 'FETCH_HEAD'],
                         cwd=dest,

src/pip/_internal/vcs/mercurial.py

@@ -97,7 +97,7 @@ class Mercurial(VersionControl):
         current_rev_hash = self.get_revision_hash(location)
         return '%s@%s#egg=%s' % (repo, current_rev_hash, egg_project_name)
 
-    def check_version(self, dest, rev_options):
+    def check_version(self, dest, commit_id):
         """Always assume the versions don't match"""
         return False
 

src/pip/_internal/vcs/subversion.py

@@ -217,7 +217,7 @@ class Subversion(VersionControl):
         rev = self.get_revision(location)
         return 'svn+%s@%s#egg=%s' % (repo, rev, egg_project_name)
 
-    def check_version(self, dest, rev_options):
+    def check_version(self, dest, commit_id):
         """Always assume the versions don't match"""
         return False
 

tests/unit/test_vcs.py

@@ -118,16 +118,15 @@ def test_git_get_src_requirements(git, dist):
     ])
 
 
-@pytest.mark.parametrize('ref,result', (
+@pytest.mark.parametrize('commit,result', (
     ('5547fa909e83df8bd743d3978d6667497983a4b7', True),
     ('5547fa909', False),
     ('5678', False),
     ('abc123', False),
     ('foo', False),
 ))
-def test_git_check_version(git, ref, result):
-    rev_options = git.make_rev_options(ref)
-    assert git.check_version('foo', rev_options) is result
+def test_git_check_version(git, commit, result):
+    assert git.check_version('/path', commit) is result
 
 
 def test_translate_egg_surname():