tree fa4629fcddd7fa6ebfdbb92113827559f03f906c
parent c2e94066cf35c9ed33fe694ef8b14ab984752896
author Youssef Elghareeb <ghareeb@google.com> 1649686626 +0200
committer Youssef Elghareeb <ghareeb@google.com> 1649762129 +0200

Don't update the cache-automerge ref while requesting diffs

In change I430ac9bf30, we made the computation of the auto-merge commit
synchronous on change/PS creation. The computation creates the
auto-merge and updates the cache-automerge ref.

The redesigned diff cache requires both old/new commits to be present in
the repository (see I817df9061 for context). For this we updated
BaseCommitUtil (class that computes the base commit before requesting
diffs from the cache) to always compute and persist the auto-merge
commit and also update the cache-automerge ref.

We've seen occasionnal errors while performing git push due to a lock
failure on the cache auto-merge ref. This is due to two sets of callers
trying to update this ref:
  * The change / PS creation path
  * A simultaneous diff request

To fix this, we update BaseCommitUtil and drop the ref update, but the
auto-merge commit is still computed. This means the auto-merge will be
computed each time a diff is requested, but this shouldn't happen since
the other path (PS / change creation) will trigger the ref update.

Google-Bug-Id: b/204154755
Release-Notes: skip
Change-Id: Ieafe0feeba932b5f35096d4b5de19373658129aa