Sample case: ``` git clone https://github.com/golang/go.git cd go git config core.commitGraph true git commit-graph write --split --reachable --changed-paths git checkout 3730814f2f2bf24550920c39a16841583de2dac1 # Reproduce HEAD # Observe that there are no commits to this file until 53fd522 time git rev-list -1 HEAD -- test/index0.go # 0.07s # Check size of test/index0.go and of 53fd522's diff wc -l test/index0.go # 12 git show --stat 53fd522c0db58f3bd75d85295f46bb06e8ab1a9b -- test/index0.go # 1 line modified # Find commit 53fd522 with --follow enabled time git log --pretty=format:%H --follow --max-count=1 HEAD -- test/index0.go # 2.3s (!) ``` As far as I can tell, even with all of git's expensive rename and copy heuristics, the above call shouldn't take this long (nor should higher max-counts, but count 1 is easier to ballpark the work required): - There are no other commits touching this file after the target commit. - Even if some commit after the target commit copied index0.go to another file, such a commit would not need to be included in index0.go's log, so there should be no need to do any sort of copy-checking work until index0.go is touched. - The target commit is not the creation of the file nor is it a > 50% rewrite of the file, so it should not be possible for it to count as a rename or copy, and therefore no other file blobs should need to be checked to confirm this (also, we only requested one commit, so even if the target commit were a rename, in theory there would be no need to check this). I assume one or more of the following are going on: - I'm missing some nuance / reason why rename/copy detection is necessarily more expensive than I think, even for commits that don't touch the file - --follow is not taking advantage of the commit graph (seems likely as --follow seems equally slow with core.commitGraph off) - --follow is performing expensive rename/copy checks even on small diffs that are not file creations - --follow is not using the --max-count target to limit its work - --follow is not using the --format output to limit its work? (Are there format options that require more work?) Git version: 2.50.0.714.g196bf9f422-goog
