Improve Garbage collection in Bitbucket

Issue Summary

The repository size grows from time to time. But the Garbage collection in Bitbucket fails to do the necessary cleanup. It's almost like the GC starts, but does nothing and the size grows every day.

When we create a fork to the repository, delete it and does a dummy push, it triggers garbage collection in Bitbucket and it cleans up without deleting any necessary files. This saves a lot of space while the regular garbage collection cleans up very little space.

Steps to Reproduce

The issue was not reproducible in the test instance. But this was observed in the customer's production environment where there are thousands of repositories that are constantly used. 

• We have more than 10k repositories in Bitbucket
• More than 100 are larger than 1 GB

Expected Results

Bitbucket Garbage collection keeps their size in check.

Actual Results

There are no visible changes in size after Bitbucket Garbage collection get executed and the size of the repository keeps growing every day.

From gc logs, we can see only the pack operations are performed. The other GC operations such as repack or prune operations are not performed.

Workaround

Create a fork to the repository, delete it and do a dummy push. This will trigger the prune operation and can reduce the size considerably, without removing any wanted files.