Assigns None instead of 'na' git_* properties

If the workspace directory does not reside within a git repository,
assign 'None' to PopperConfig.git_* properties. This in turns results in
not defining GIT_* environment variables at all when executing a
workflow.

fixes #823

cli/popper/scm.py

@@ -164,7 +164,7 @@ def get_sha(repo, short=None):
     first 7 characters, otherwise it returns the entire SHA1 string.
     """
     if not repo:
-        return 'na'
+        return None
 
     if short:
         return repo.git.rev_parse(repo.head.object.hexsha, short=short)
@@ -178,7 +178,7 @@ def get_branch(repo):
     GIT_BRANCH (Jenkins), CIRCLE_BRANCH and CI_COMMIT_REF_NAME (Gitlab)
     """
     if not repo:
-        return 'na'
+        return None
 
     if not repo.head.is_detached:
         return repo.active_branch.name
@@ -195,3 +195,5 @@ def get_branch(repo):
     branch = os.environ.get('CI_COMMIT_REF_NAME')
     if branch:
         return branch
+
+    return get_sha(repo)

cli/test/test_config.py

@@ -53,9 +53,9 @@ def test_config_non_defaults(self):
 
     def test_config_without_git_repo(self):
         conf = PopperConfig(workspace_dir='/tmp/foo')
-        self.assertEqual('na', conf.git_commit)
-        self.assertEqual('na', conf.git_branch)
-        self.assertEqual('na', conf.git_sha_short)
+        self.assertIsNone(conf.git_commit)
+        self.assertIsNone(conf.git_branch)
+        self.assertIsNone(conf.git_sha_short)
 
     def test_config_with_git_repo(self):
         r = self.mk_repo()

cli/test/test_scm.py

@@ -27,6 +27,7 @@ def test_get_remote_url(self):
 
     def test_get_branch_in_detached_head_state(self):
         repo = self.mk_repo()
+
         repo.git.checkout('HEAD~1')
 
         os.environ['TRAVIS_BRANCH'] = 'travis'
@@ -45,6 +46,13 @@ def test_get_branch_in_detached_head_state(self):
         self.assertEqual('gitlab', scm.get_branch(repo))
         os.environ.pop('CI_COMMIT_REF_NAME')
 
+        self.assertEqual(scm.get_sha(repo), scm.get_branch(repo))
+
+        # None given as arg
+        self.assertIsNone(scm.get_sha(None))
+        self.assertIsNone(scm.get_sha(None, short=8))
+        self.assertIsNone(scm.get_branch(None))
+
     def test_clone(self):
         tempdir = tempfile.mkdtemp()
         tdir = os.path.join(tempdir, 'test_clone')