By default gerrit replication pushes +refs/*:refs/*, which includes
refs/changes. For large repositories that potentially means hundreds
of thousands of references.
Per-repo git mirroring does not push refs/changes, so when it runs it
ends up deleting those references, which can take a long time, blocking
the executor.
To fix that, we should:
- stop pushing refs/changes to GitHub (this change)
- delete refs/changes on GitHub repositories, asynchronously
- enable per-repo replication
- disable Gerrit-wide replication
NB: it is unclear if Gerrit replication would start deleting the
extraneous references on remote GitHub repositories once this
merges. If this is the case, since replication is limited to a
single thread (default value for 'threads') and is not happening
in an executor, this should not have negative impact, beyond
potentially delaying GitHub mirroring.
Change-Id: I94f69c889c9b4418ef81b3b2ca436ba99696ba72
6935318712