Compare revisions for remote git branches/tags

news/4386.bugfix

@@ -0,0 +1,3 @@
+Adds a simple check if the local revision is the same as the remote revision, even if the ref is a tag or branch name.
+
+Until now branches or tags would always try to update the repository.

pip/vcs/__init__.py

@@ -184,7 +184,7 @@ def update(self, dest, rev_options):
         """
         raise NotImplementedError
 
-    def check_version(self, dest, rev_options):
+    def check_version(self, dest, rev_options, url=None):
         """
         Return True if the version is identical to what exists and
         doesn't need to be updated.
@@ -211,7 +211,7 @@ def check_destination(self, dest, url, rev_options, rev_display):
                         display_path(dest),
                         url,
                     )
-                    if not self.check_version(dest, rev_options):
+                    if not self.check_version(dest, rev_options, url=url):
                         logger.info(
                             'Updating %s %s%s',
                             display_path(dest),

pip/vcs/bazaar.py

@@ -108,7 +108,7 @@ def get_src_requirement(self, dist, location):
         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, rev_options, url=None):
         """Always assume the versions don't match"""
         return False
 

pip/vcs/git.py

@@ -96,14 +96,22 @@ def check_rev_options(self, rev, dest, rev_options):
             )
             return rev_options
 
-    def check_version(self, dest, rev_options):
+    def check_version(self, dest, rev_options, url=None):
         """
         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
-        or tag will never compare as True. So this ultimately only matches
-        against exact shas.
+        but current rev will always point to a sha.
+        This means that if ref is a branch or tag name,
+        we will fetch the ref's sha using ls-remote
         """
-        return self.get_revision(dest).startswith(rev_options[0])
+
+        local_revision = self.get_revision(dest)
+
+        if url is not None:
+            remote_revision = self._get_remote_revision(url, rev_options[0])
+        else:
+            remote_revision = rev_options[0]
+
+        return local_revision.startswith(remote_revision)
 
     def switch(self, dest, url, rev_options):
         self.run_command(['config', 'remote.origin.url', url], cwd=dest)
@@ -171,6 +179,12 @@ def get_revision(self, location):
             ['rev-parse', 'HEAD'], show_stdout=False, cwd=location)
         return current_rev.strip()
 
+    def _get_remote_revision(self, url, ref):
+        remote_rev = self.run_command(
+            ['ls-remote', url, ref], show_stdout=False)
+
+        return remote_rev.split()[0].strip()
+
     def get_full_refs(self, location):
         """Yields tuples of (commit, ref) for branches and tags"""
         output = self.run_command(['show-ref'],

pip/vcs/mercurial.py

@@ -96,7 +96,7 @@ def get_src_requirement(self, dist, location):
         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, rev_options, url=None):
         """Always assume the versions don't match"""
         return False
 

pip/vcs/subversion.py

@@ -215,7 +215,7 @@ def get_src_requirement(self, dist, location):
         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, rev_options, url=None):
         """Always assume the versions don't match"""
         return False
 

tests/functional/test_install_vcs_git.py

@@ -74,6 +74,16 @@ def test_check_version(script):
     assert not git.check_version(version_pkg_path, ['branch0.1'])
     assert not git.check_version(version_pkg_path, ['abc123'])
 
+    # Make sure check_version compares remote urls correctly
+    assert git.check_version(version_pkg_path, ['master'], url='file://%s' % version_pkg_path)
+
+    script.run(
+        'git', 'commit', '--allow-empty', '-m ""',
+        cwd=version_pkg_path
+    )
+
+    assert not git.check_version(version_pkg_path, ['branch0.1'], url='file://%s' % version_pkg_path)
+
 
 @patch('pip.vcs.git.Git.get_short_refs')
 def test_check_rev_options_should_handle_branch_name(get_refs_mock):