After pushing, wait for MRs to stabilize

By stabililze we mean that the "changes_count" field of the MR has a
value of "1".  This ensures that by the time the "git lab" command
terminates, MRs should be fully up-to-date.

Note that this approach will have to be reevaluated if #16 is
implemented (which would allow multiple commits to end up in a single
MR).

Also:
 unit_tests/merge_request_test.py:
  MergeRequestTest:
   Removed WAIT_TIME_BEFORE_VALIDATE, etc since create_merge_requests()
   now waits for the desired state before returning.

Change-Id: Id20d9feb27076afe0603bee334badc815e5528a9

gerritlab/main.py

@@ -181,6 +181,10 @@ def create_merge_requests(repo, remote, local_branch):
     with timing("push"):
         remote.push(refspec=refs_to_push, force=True)        
 
+    with timing("stabilize"):
+        for mr in new_mrs+updated_mrs:
+            mr.wait_until_stable()
+
     if len(updated_mrs) == 0 and len(new_mrs) == 0:
         print()
         warn("No updated/new MRs.\n")

gerritlab/merge_request.py

@@ -33,6 +33,9 @@ def __init__(
         self._web_url = None
         self._mergeable = False
 
+        self._set_data(json_data)
+
+    def _set_data(self, json_data):
         if json_data is not None:
             for attr in json_data:
                 setattr(self, "_{}".format(attr), json_data[attr])
@@ -157,6 +160,25 @@ def needs_update(self, commit) -> bool:
                 self._title != title or 
                 self._description != desc.strip())
 
+    def refresh(self):
+        """
+        Update's this object's data using the latest info available from the server.
+        """
+        r = global_vars.session.get("{}/{}".format(global_vars.mr_url, self._iid))
+        r.raise_for_status()
+        self._set_data(r.json())
+
+    def wait_until_stable(self):
+        """
+        Poll GitLab until the changes_count field has a value of "1".
+        Other values indicate that GitLab hasn't reacted to a push yet.
+        """
+        while True:
+            self.refresh()
+            if self._changes_count == "1":
+                return
+            time.sleep(0.500)
+
 
 def _get_open_merge_requests():
     """Gets all open merge requests in the GitLab repo."""

unit_tests/merge_request_test.py

@@ -20,11 +20,6 @@
 EMAIL = "[email protected]"
 
 class MergeRequestTest(unittest.TestCase):
-    # GitLab seems to need a little bit of time before the commits of the
-    # MRs get updated, after new commits are pushed to the branches. This is
-    # the time (in seconds) we'll wait before we validate the MRs.
-    WAIT_TIME_BEFORE_VALIDATE = 10
-
     def setUp(self):
         self._test_project_dir = os.path.join(
             repo_path, GITLAB_TEST_PROJECT_PATH)
@@ -40,7 +35,6 @@ def setUp(self):
         self._local_branch = LOCAL_BRANCH
         self._test_repo.git.checkout(self._local_branch)
         global_vars.ci_mode = True
-        self._wait_before_validate = True
         self._mrs = []
 
     def tearDown(self):
@@ -116,12 +110,6 @@ def validate_mr(mr, commit, target_branch):
             self._mrs.append(
                 merge_request.get_merge_request(self._remote, source_branch))
 
-        # Wait some time before the validation, in order for GitLab to update
-        # the MRs after seeing new commits.
-        if self._wait_before_validate:
-            time.sleep(MergeRequestTest.WAIT_TIME_BEFORE_VALIDATE)
-            self._wait_before_validate = False
-
         for idx, (mr, commit) in enumerate(zip(self._mrs, commits)):
             validate_mr(
                 mr, commit, global_vars.global_target_branch if idx == 0 else