tree 20fc329eb4d4f2083e3c244a4d776b8906db8227
parent b6e53e6ec3d09e7e6a8dd328f60ccee243f0aa57
author Edwin Kempin <ekempin@google.com> 1581065056 +0100
committer Edwin Kempin <ekempin@google.com> 1581067786 +0000

CheckMergeability: Do not fail with 500 ISE on NoMergeBaseException

If NoMergeBaseException is thrown it's the state of the repository that
prevents the merge (e.g. the reason is
CONFLICTS_DURING_MERGE_BASE_CALCULATION). We should return '409
Conflict' in this case as we do in other REST endpoints.

It would be better to return a MergeableInfo with mergeable = false, but
if we do that now the caller cannot find out the reason why the change
is not mergeable since MergeableInfo doesn't have any field to carry a
message or a reason. We could add this field, but then the frontend also
needs to be adapted to show that message to the user. That's more work
that we leave for later. For now returning '409 Conflict' is better than
failing with '500 Internal Server Error'.

Change-Id: I307aab2bd94495634c77eda0976dea435673bdcb
Signed-off-by: Edwin Kempin <ekempin@google.com>