Make git hooks run ktlint on changed files only

[francescocervone]

It would be great if the git hooks provided by ktlint via installGitPreCommitHook/installGitPrePushHook were made for executing on git diff only.

Expected Behavior

ktlint git pre-commit and pre-push hooks run on changed files only.

Current Behavior

ktlint git pre-commit and pre-push hooks run on all files of the current directory.
For instance, when I install the pre-commit hook via ktlint installGitPreCommitHook, it looks like this:

git diff --name-only --cached --relative | grep '\.kt[s"]\?$' | xargs ktlint --relative .

As you can see, the first command lists changed files, then only kt[s] files are selected, and finally they are piped into the ktlint command. Unfortunately, last argument of the ktlint command is the current directory, meaning that in addition to changed files, also the entire current directory is going to be checked. Basically, the current directory "overrides" the piped git diff files.

Additional information

• Current version of ktlint: 0.43.2
• Looks like ktlint's git hooks have never changed, but I observed a performance decrease from version 0.40 to 0.41 and higher (see 0.41.0 Performance decrease #1135 (comment)). This performance decrease brought me here.

[adriafernandez]

Hi there! Has someone achieved this behavior??

[paul-dingemans]

Have you tried to generate new git hooks with latest version of Kltint CLI:

ktlint/ktlint-cli/src/main/kotlin/com/pinterest/ktlint/cli/internal/GitPreCommitHookSubCommand.kt

Line 23 in 7c653cf

git diff --name-only -z --cached --relative -- '*.kt' '*.kts' | ktlint --relative --patterns-from-stdin=''