indexer may miss repository changes

Just observed on a dogfood instance (fisheye.diac) on git repository, but same may potentially happen on other SCMs too, most likely Mercurial. Indexer may not notice repository changes and won't index them until new changes appear in the remote repository. Manually triggering incremental index won't help too.

Most likely scenario that occured:

1. new changes were pushed to remote git repository
2. FishEye started indexing them, first step is to run fetch to update local clone (this seems to have finished correctly)
3. next step is to compare branches and tags in local repository against heads in remote repository. But FishEye was restarted at this point (notice local clone was updated already)
4. after restart on every incremental index scan FishEye repeats steps 2 and 3. Until step 2 brings new changes step 3 would assess that local and remote heads are the same and there is nothing to be indexed.

Workaround

Push any changes to remote repository to recover