GitCommitBear.py: Require URL in commit body

This ensures that the git commit contains a URL
that relates to an issue.

Fixes coala#1112

.coafile

@@ -29,6 +29,7 @@ bears = SpaceConsistencyBear
 
 [commit]
 bears = GitCommitBear
+host_site = github
 shortlog_trailing_period = False
 shortlog_regex = ([^:]*|[^:]+: [A-Z0-9*].*)
 

bears/vcs/git/GitCommitBear.py

@@ -3,6 +3,8 @@
 import shutil
 import os
 
+from urllib.parse import urlparse
+
 from coalib.bears.GlobalBear import GlobalBear
 from coalib.bears.requirements.PipRequirement import PipRequirement
 from coala_utils.ContextManagers import change_directory
@@ -175,6 +177,7 @@ def check_imperative(self, paragraph):
     def check_body(self, body,
                    body_line_length: int=72,
                    force_body: bool=False,
+                   host_site: str='',
                    ignore_length_regex: typed_list(str)=()):
         """
         Checks the given commit body.
@@ -183,6 +186,8 @@ def check_body(self, body,
         :param body_line_length:    The maximum line-length of the body. The
                                     newline character at each line end does not
                                     count to the length.
+        :param host_site:           The website used for hosting the git
+                                    repository.
         :param force_body:          Whether a body shall exist or not.
         :param ignore_length_regex: Lines matching each of the regular
                                     expressions in this list will be ignored.
@@ -197,6 +202,34 @@ def check_body(self, body,
                                'HEAD commit. Please add one.')
             return
 
+        # Git keywords for closing issues
+        # https://help.github.com/articles/closing-issues-via-commit-messages/
+        git_keys = """close closes closed
+                      fix fixes fixed
+                      resolve resolves resolved""".split()
+
+        body_string = '\n'.join(body).lower()
+        if host_site != '' and any(key in body_string for key in git_keys):
+            urls = re.findall(r'(https?://\S+)', body_string)
+            good_url = False
+            for url in urls:
+                pieces = urlparse(url)
+                netloc = pieces.netloc
+                scheme = pieces.scheme
+                path = pieces.path
+                try:
+                    assert all([scheme, netloc, path])
+                except AssertionError:
+                    pass
+                if netloc.find(host_site) != -1 and path.find('issues') != -1:
+                    good_url = True
+
+            if not good_url:
+                yield Result(self, 'No issue related URL found in '
+                                   'the body at HEAD commit. '
+                                   'Please add one.')
+                return
+
         ignore_regexes = [re.compile(regex) for regex in ignore_length_regex]
         if any((len(line) > body_line_length and
                 not any(regex.search(line) for regex in ignore_regexes))

tests/vcs/git/GitCommitBearTest.py

@@ -267,6 +267,31 @@ def test_body_checks(self):
                          [])
         self.assertTrue(self.msg_queue.empty())
 
+        # Commit has neither keywords nor issues
+        self.git_commit('Shortlog\n\n'
+                        'This line is ok.\n'
+                        'This line is by far too long (in this case).\n'
+                        'This one too, blablablablablablablablabla.')
+        self.assertEqual(self.run_uut(host_site='github',), [])
+
+        # Host site chosen and has an issue
+        self.git_commit('Shortlog\n\n'
+                        'First line, blablablablablabla.\n'
+                        'Another line, blablablablablabla.\n'
+                        'Fix https://github.com/user/repo/issues/someissue')
+        self.assertEqual(self.run_uut(host_site='github',), [])
+
+        # Host site chosen and has keywords but no url
+        self.git_commit('Shortlog\n\n'
+                        'First line, blablablablablabla.\n'
+                        'Another line, blablablablablabla.\n'
+                        'Fix #123')
+        self.assertEqual(self.run_uut(host_site='github',),
+                         ['No issue related URL found in '
+                          'the body at HEAD commit. '
+                          'Please add one.'])
+        self.assert_no_msgs()
+
     def test_different_path(self):
         no_git_dir = mkdtemp()
         self.git_commit('Add a very long shortlog for a bad project history.')