Spread the operation of querying which local branches exist across a
pool of processes and build the name map of projects -> branches as
these tasks finish rather than blocking on the entire query. The search
operations are submitted in batches to reduce the overhead of interprocess
communication. The `chunksize` argument used to control this batch size
was selected by incrementing through powers of two until it stopped being
faster.
Change-Id: Ie3d7f799ee8e83e5058536caf53e2979175408b7
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/291342
Tested-by: Chris Mcdonald <cjmcdonald@google.com>
Reviewed-by: Mike Frysinger <vapier@google.com>
8add62325d