Why are my git rebases slow now?

During the reworking and cleanup of a rather large feature branch, I noticed that some operations were fast and others were slow but didn’t think much of it and kept squashing and re-arranging. Until I happened to notice the 359% CPU usage for 1Password in Activity Monitor.

I had started to sign my commits using 1Password quite some time ago¹ and in the day to day business you don’t notice it much. But this time, squashing two commits on a 400-ish commit branch took like several tens of seconds.

So I disabled it just for the repository with:

$ git config commit.gpgsign false

And behold! It was fast again (as in a tiny fraction of a second). I should have known because I have worked with larger codebases and change sets on less capable machines and do remember it to be as fast, but I reckon you get gradually used to it and then loose your own baseline.

Giving your git repository a good scrub

Don’t forget to append a --prune to your fetches and do a git gc --aggressive² every now and then. Especially so when you create tens of thousands of temporary commits during a large rebase/cleanup.