GitCommitBear.py: Detect revert commits

This detects revert commits
and checks they have a reason as well.

Closes #337

bears/vcs/git/GitCommitBear.py

@@ -96,7 +96,9 @@ def get_host_from_remotes():
             netloc = urlparse(url)[1]
         return netloc.split('.')[0]
 
-    def run(self, allow_empty_commit_message: bool = False, **kwargs):
+    def run(self, allow_empty_commit_message: bool = False,
+            check_revert_commits: bool = True,
+            **kwargs):
         """
         Check the current git commit message at HEAD.
 
@@ -105,6 +107,8 @@ def run(self, allow_empty_commit_message: bool = False, **kwargs):
 
         :param allow_empty_commit_message: Whether empty commit messages are
                                            allowed or not.
+        :param check_revert_commits: whether revert commits are to be
+                                            checked or not.
         """
         with change_directory(self.get_config_dir() or os.getcwd()):
             stdout, stderr = run_shell_command('git log -1 --pretty=%B')
@@ -123,6 +127,9 @@ def run(self, allow_empty_commit_message: bool = False, **kwargs):
                 yield Result(self, 'HEAD commit has no message.')
             return
 
+        if shortlog.startswith('Revert') and check_revert_commits:
+            yield Result(self, 'Revert commit does not have a reason.')
+
         yield from self.check_shortlog(
             shortlog,
             **self.get_shortlog_checks_metadata().filter_parameters(kwargs))

tests/vcs/git/GitCommitBearTest.py

@@ -125,6 +125,14 @@ def test_empty_message(self):
                          [])
         self.assert_no_msgs()
 
+    def test_revert_commit(self):
+        self.git_commit('Revert : identifies revert commit\n')
+
+        self.assertEqual(self.run_uut(),
+                         ['Revert commit does not have a reason.'])
+
+        self.assert_no_msgs()
+
     @unittest.mock.patch('bears.vcs.git.GitCommitBear.run_shell_command',
                          return_value=('one-liner-message\n', ''))
     def test_pure_oneliner_message(self, patch):