Published on 2017-09-07
When encountering issues like:
Cloning repository...
Cloning into '/builds/username/repo_name'...
fatal: pack is corrupted (SHA1 mismatch)
fatal: index-pack failed
ERROR: Job failed: exit code 1
Run git gc --aggressive and/or git repack -a -d -f --depth=50 --window=250
on the origin repository. If you are using a system like Gitlab / GitlabCI,
manually trigger the Housekeeping routine.
Central repositories can have git index corruption and other slowness operations due to fragmentation and high numbers of objects in a git repository. By deleting merged branches, using only lightweight tags for references (instead of, say release branches), and squashing merges into a single commit, we reduce the total number of objects git is required to manage.
Normally, git will automatically collect unused references, but the incremental GC operations don't regularly go back and rebuild or repack the repository data. These manual invocations of git gc/repack will resolve the issue.