Use multiprocessing to run in parallel. When operating on multiple
projects, this can greatly speed things up. Across 1000 repos, it
goes from ~40sec to ~16sec with the default -j8.
The output processing does not appear to be a significant bottle
neck -- it accounts for <1sec out of the ~16sec runtime. Thus we
leave it in the main thread to simplify the code.
Change-Id: I750b72c7711b0c5d26e65d480738fbaac3a69971
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/297984
Reviewed-by: Chris Mcdonald <cjmcdonald@google.com>
Tested-by: Mike Frysinger <vapier@google.com>
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