I only understood what "Stash" is in this situation after your comment. Looks like it is an Atlassian product that was renamed: https://confluence.atlassian.com/bitbucketserver/bitbucket-r...
Funny that they don't mention the name collision as reason for renaming it...
I'll say it was with the configuration and the buggy implementation of squash merging button with Stash.
After replacing the repo, people were amazed with how fast it was. Also apparently I became notorious as the committer of the whole repository, since first commit was mine!
As an aside, I find myself doing amend commits all the time these days.
I did't even thought about it. In fact, those are hundreds of lines that no one would read, as the commits are lost and you can't do anything with them...
I hadn't even heard of squash commits before this, and we looked into it because the Stash site kept timing out. All the people that had built it was just shrug, Stash sucks, always been this way, like all seniors-that-are-actually-juniors-because-big-corp-can't-keep-good-folks-to-teach-them do. I mean maybe the tool sucks, but at least give it a fair chance first.
The result: the git repository (at least in Stash) slowed to a crawl, because the comments to the commits were several hundred MiB. It was nuts. Never seen a git hosting site go that slow before.
Actually had to replace the whole repo with another, more or less wiping history (kept the old slow repo just in case, of course), and disabling that damn squash-merge button.