Please add back the mention of the reverted commit to the commit message:

This commit reverts ef3ed45c1240197b721f38a01ec48e7dc6e7c179

Good point, I assumed that GitHub would do that for me.

This wasn't "just a performance optimisation", it made nix-gitignore actually usable on non-toy repos.
Without these changes memory & CPU usage is simply so bad that nix-gitignore is unusable.

See #106172 (comment) for an example of a behaviour change. It appears that negative patterns were not working correctly.

Is breaking negative patterns fundamental to the performance improvement? If so maybe the new functions should be added under a new name? If not then a fix that preserves support for negative patterns is very welcome.

If the optimized code cannot be fixed to take negative patterns into account it is still possible to do as follows

• if there are any negative patterns
• then use the old slow code
• else use the new shiny code