[hood]

In explorer/watch.lua, is_git executes for every directory node assigned a filesystem watcher.

Previously, even when GIT_DIR was unset, the function invoked expensive Vimscript evaluations, calling vim.fn.fnamemodify(path, ":p"), fnamemodify(nil, ":p"), and fnamemodify(path, ":t") on every check 🫠 .

This change basically guards the GIT_DIR resolution behind an environment check and replaces fnamemodify(..., ":t") with path extraction in pure lua, eliminating the Vimscript round-trips during directory scanning.

I thought we could even cache GIT_DIR, but that would expose us to the risk of not catching up if the env var gets changed at runtime, uncommon but better safe than sorry 🤷 .

Note I used utils.path_basename(path) as the lua equivalent of fnamemodify(path, ":t”), as I already noticed this was its use in the pre-existing codebase.

Measured impact:

• is_git across ~1,5k directories dropped from ~130 ms down to ~2.5 ms (~50x speedup) (!!)
• Output remains 1:1 with that’s currently running on master

AI usage: Claude Code (Opus 5.5) helped on self-review, code cleanup and most importantly measuring the impact.

Tested on macOS nvim-dev 0.13, untested on Windows (though path_basename relies on package.config path separators), Linux, Neovim 0.10/0.11, and scenarios where GIT_DIR is explicitly defined.

resolves #3384

[alex-courtis]

This is great, thank you for your contribution.

Manual testing with log profile modified to track us:

Arch linux on ext4. linux source repo with max_folder_discovery = 5000

~8ms reduction for E

master

: ; grep "END.*is_git" $XDG_STATE_HOME/nvim/nvim-tree.log | sed -E 's/.*([0-9]+)us/\1/g' | paste -sd+ | bc
21555

: ; grep "END.*is_git" $XDG_STATE_HOME/nvim/nvim-tree.log | sed -E 's/.*([0-9]+)us/\1/g' | paste -sd+ | bc
21562

: ; grep "END.*is_git" $XDG_STATE_HOME/nvim/nvim-tree.log | sed -E 's/.*([0-9]+)us/\1/g' | paste -sd+ | bc
21376

branch

: ; grep "END.*is_git" $XDG_STATE_HOME/nvim/nvim-tree.log | sed -E 's/.*([0-9]+)us/\1/g' | paste -sd+ | bc
13027

: ; grep "END.*is_git" $XDG_STATE_HOME/nvim/nvim-tree.log | sed -E 's/.*([0-9]+)us/\1/g' | paste -sd+ | bc
12781

: ; grep "END.*is_git" $XDG_STATE_HOME/nvim/nvim-tree.log | sed -E 's/.*([0-9]+)us/\1/g' | paste -sd+ | bc
12947

[alex-courtis]

Please refrain from comments like these: it's only relevant to explain this change and it doesn't add any value for future maintainers.

[hood]

true, this was more of self-reminder i forgot to amend, mb. removed now

[alex-courtis]

I thought we could even cache GIT_DIR, but that would expose us to the risk of not catching up if the env var gets changed at runtime, uncommon but better safe than sorry 🤷 .

That's sensible. We've had several issues in the past where we were too aggressive on git caching.

[alex-courtis]

• is_git across ~1,5k directories dropped from ~130 ms down to ~2.5 ms (~50x speedup) (!!)

In the future please provide instructions for performance testing an replication, to lessen the burden of review.

[hood]

Thank you a lot for reviewing, @alex-courtis ❤️ !

Though, and please correct me if i'm wrong, I think I spotted an issue with your measurements: I think the sed is under-reporting. That greedy .* swallows all but the last digit, so each line contributes only its final digit.

Repro of the issue: echo '... END is_git /a/b 1234us' | sed -E 's/.*([0-9]+)us/\1/g’
This should measure correclty: grep "END.*is_git" $XDG_STATE_HOME/nvim/nvim-tree.log | sed -E 's/.* ([0-9]+)us$/\1/' | paste -sd+ | bc

[alex-courtis]

Thank you a lot for reviewing, @alex-courtis ❤️ !

Though, and please correct me if i'm wrong, I think I spotted an issue with your measurements: I think the sed is under-reporting. That greedy .* swallows all but the last digit, so each line contributes only its final digit.

Repro of the issue: echo '... END is_git /a/b 1234us' | sed -E 's/.*([0-9]+)us/\1/g’ This should measure correclty: grep "END.*is_git" $XDG_STATE_HOME/nvim/nvim-tree.log | sed -E 's/.* ([0-9]+)us$/\1/' | paste -sd+ | bc

Good catch!

With the correct regex:

master:

: ; grep "END.*is_git" $XDG_STATE_HOME/nvim/nvim-tree.log | sed -E 's/.* ([0-9]+)us/\1/g' | paste -sd+ | bc
21613
: ; grep "END.*is_git" $XDG_STATE_HOME/nvim/nvim-tree.log | sed -E 's/.* ([0-9]+)us/\1/g' | paste -sd+ | bc
23265
: ; grep "END.*is_git" $XDG_STATE_HOME/nvim/nvim-tree.log | sed -E 's/.* ([0-9]+)us/\1/g' | paste -sd+ | bc
23367

branch:

: ; grep "END.*is_git" $XDG_STATE_HOME/nvim/nvim-tree.log | sed -E 's/.* ([0-9]+)us/\1/g' | paste -sd+ | bc
13589
: ; grep "END.*is_git" $XDG_STATE_HOME/nvim/nvim-tree.log | sed -E 's/.* ([0-9]+)us/\1/g' | paste -sd+ | bc
12961
: ; grep "END.*is_git" $XDG_STATE_HOME/nvim/nvim-tree.log | sed -E 's/.* ([0-9]+)us/\1/g' | paste -sd+ | bc
13107

[alex-courtis]

I'm really happy with this PR and the issues you have raised, which will enable great performance increases for the tree. Your descriptions are well written and readable.

PRs for all those issues would be most gratefully appreciated.

Please remember:

• I'm quite limited in time and will review PRs as time becomes available
• to follow the bug report template when raising issues so that a reproducer test environment may be quickly set up during review.