AddNewlineAction: New action for GitCommitBear

This adds a new action which adds a newline between
shortlog and body of commit message when applied.
This also make changes in CommitBear.py to pass
AddNewlineAction when Result is yielded.

bears/vcs/CommitBear.py

@@ -14,6 +14,7 @@
 from coalib.settings.FunctionMetadata import FunctionMetadata
 from dependency_management.requirements.PipRequirement import PipRequirement
 from bears.vcs.actions.EditCommitMessageAction import EditCommitMessageAction
+from bears.vcs.actions.AddNewlineAction import AddNewlineAction
 
 
 class _CommitBear(GlobalBear):
@@ -280,7 +281,8 @@ def check_body(self, body,
             yield Result(self,
                          'No newline found between shortlog and body at '
                          'HEAD commit. Please add one.',
-                         actions=[EditCommitMessageAction()])
+                         actions=[EditCommitMessageAction(),
+                                  AddNewlineAction()])
             return
 
         if body_regex and not re.fullmatch(body_regex, body.strip()):

bears/vcs/actions/AddNewlineAction.py

@@ -0,0 +1,35 @@
+from coalib.misc.Shell import run_shell_command
+from coalib.results.result_actions.ResultAction import ResultAction
+
+
+class AddNewlineAction(ResultAction):
+    """
+    Adds a newline between shortlog and body of the commit message
+    of the HEAD commit.
+    """
+
+    SUCCESS_MESSAGE = 'New Line added successfully.'
+
+    def is_applicable(self,
+                      result,
+                      original_file_dict,
+                      file_diff_dict,
+                      applied_actions=()):
+        new_message, _ = run_shell_command('git log -1 --pretty=%B')
+        new_message = new_message.rstrip('\n')
+        pos = new_message.find('\n')
+        self.shortlog = new_message[:pos] if pos != -1 else new_message
+        self.body = new_message[pos+1:] if pos != -1 else ''
+        if self.body[0] != '\n':
+            return True
+        else:
+            return False
+
+    def apply(self, result, original_file_dict, file_diff_dict):
+        """
+        Add New(L)ine [Note: This may rewrite your commit history]
+        """
+        new_commit_message = '{}\n\n{}'.format(self.shortlog, self.body)
+        command = 'git commit -o --amend -m "{}"'.format(new_commit_message)
+        stdout, err = run_shell_command(command)
+        return file_diff_dict

tests/vcs/actions/AddNewlineActionTest.py

@@ -0,0 +1,96 @@
+import unittest
+import os
+import platform
+import shutil
+from tempfile import mkdtemp, mkstemp
+from unittest.mock import Mock
+
+from coalib.results.Result import Result
+from bears.vcs.actions.AddNewlineAction import AddNewlineAction
+from coala_utils.ContextManagers import retrieve_stdout
+from coalib.misc.Shell import run_shell_command
+
+
+class AddNewlineActionTest(unittest.TestCase):
+
+    @staticmethod
+    def run_git_command(*args, stdin=None):
+        return run_shell_command(' '.join(('git',) + args), stdin)
+
+    def setUp(self):
+        self.shortlog = 'file.py: Add something'
+        self.body = ('Added something, wrote some things\n'
+                     'Wrote tests\n'
+                     '\n'
+                     'Fixes #issue')
+        self.uut = AddNewlineAction()
+        self.result = Result('origin', 'message')
+
+        # Creating a temporary git repository and
+        # adding a commit to test
+        self._old_cwd = os.getcwd()
+        self.gitdir = mkdtemp()
+        os.chdir(self.gitdir)
+        self.gitfile = mkstemp(dir=self.gitdir)
+        self.run_git_command('init')
+        self.run_git_command('config', 'user.email coala@coala.io')
+        self.run_git_command('config', 'user.name coala')
+        self.msg = self.shortlog + '\n' + self.body
+        self.run_git_command('add .')
+        self.run_git_command('commit',
+                             '--file=-',
+                             stdin=self.msg)
+
+    def tearDown(self):
+        # Deleting the temporary repository
+        os.chdir(self._old_cwd)
+        if platform.system() == 'Windows':
+            onerror = self._windows_rmtree_remove_readonly
+        else:
+            onerror = None
+        shutil.rmtree(self.gitdir, onerror=onerror)
+
+    def test_is_applicable_apply(self):
+        # Applicable because there is no newline between shortlog and body
+        self.assertTrue(self.uut.is_applicable(self.result, {}, {}))
+
+        with retrieve_stdout() as stdout:
+            self.uut.apply(self.result, {}, {})
+            new_message, _ = run_shell_command('git log -1 --pretty=%B')
+            new_message = new_message.rstrip('\n')
+            self.assertEqual(new_message,
+                             self.shortlog + '\n\n' + self.body)
+            self.assertEqual(stdout.getvalue(), '')
+
+        # Not applicable after action is applied
+        self.assertFalse(self.uut.is_applicable(self.result, {}, {}))
+
+        # Undoing the amend done by applying the action
+        self.run_git_command('commit',
+                             '--amend',
+                             '--file=-',
+                             stdin=self.msg)
+
+    def test_is_applicable_edited_message(self):
+        # Applicable because there is no newline between shortlog and body
+        self.assertTrue(self.uut.is_applicable(self.result, {}, {}))
+
+        # Mocking EditCommitMessageAction to test cases where user first
+        # changes commit message by appying EditCommitMessageAction, then
+        # checking the applicability of AddNewlineAction
+        EditCommitMessageAction = Mock()
+        edited_msg1 = ('This is new commit message\n'
+                       'Still no new line')
+        edited_msg2 = ('This is lastest commit message\n'
+                       '\n'
+                       'Finally a new line!!')
+
+        EditCommitMessageAction.apply.side_effect = self.run_git_command(
+            'commit', '--amend', '--file=-', stdin=edited_msg1)
+        EditCommitMessageAction.apply()
+        self.assertTrue(self.uut.is_applicable(self.result, {}, {}))
+
+        EditCommitMessageAction.apply.side_effect = self.run_git_command(
+            'commit', '--amend', '--file=-', stdin=edited_msg2)
+        EditCommitMessageAction.apply()
+        self.assertFalse(self.uut.is_applicable(self.result, {}, {}))