jj squash takes 10+m is this expected?

[OGKevin]

I've managed to get myself into a situation where I have ~50 stacked commits, where the last 45 are conflicted.

The issue now is, when I refine commit 1, and want to squash changes into it, this operation takes a long time:

- 7c2ca9a7f042 kevin@hostname default@ 18 minutes ago, lasted 12 minutes
│  squash commits into 78a34b4af31a127c74f453f58f6b1c6c9ff7f4bd
│  args: jj squash -r mkqypmyy -u

I wouldn't call the repo large, I'm not experiencing anything described in #1841. It's only the squashing that takes forever. What would be steps to debug what is the bottleneck here to provide a proper bug report? My search didn't yield an issue that contains similar report. Or I'm using the wrong keywords 😭.

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It's actually any command that rewrites history, e.g. rebasing yields the same slow result.

[OGKevin]

It seems this is related to #4152