Automatically git-blame-ignore style tweaks

A post-commit hook to add an entry to .git-blame-ignore-revs for pure formatting commits

Now you can upgrade to prettier v2 without ruining git blame!

PRs with changes to .git-blame-ignore-revs cannot squash+merge, otherwise you'll have to add more entries to .git-blame-ignore-revs in a follow up PR/commit.

What does it do, how does it work?

When you make a commit like this:

style(homepage): Sort imports

This post-commit hook will automatically add another commit like so:

chore(git-blame): Ignore previous style change

Commit message may be customized in a future version to be: chore(git-blame): Ignore "Sort imports"

You do NOT need to use commitlint or commitizen to use this hook. It simply looks for commit messages starting with style: foo. (And probably also style(foo): bar, but that may come in a future version)

Setup

npm install git-blame-ignore-style-formatting-post-commit-hook --save-dev

yarn add git-blame-ignore-style-formatting-post-commit-hook --dev

If you are using husky (recommended), create hook like so:

mkdir .husky
mv .husky/post-commit .husky/old-post-commit;
rm .husky/post-commit
npx husky add .husky/post-commit 'GIT_ROOT="$(git rev-parse --show-toplevel)"';
npx husky add .husky/post-commit '$GIT_ROOT/node_modules/.bin/git-blame-ignore-style-formatting-post-commit-hook';
npx husky add .husky/post-commit '# Directly invoking module is faster than `yarn run git-blame-ignore-style-formatting-post-commit-hook`';
npx husky add .husky/post-commit "# (which makes sense, because it's skipping yarn\!)";

If not using husky, you can use this shell script as a starting point:

HOOKS_PATH=".git-hooks"
git config core.hooksPath $HOOKS_PATH
mkdir $HOOKS_PATH;
mv $HOOKS_PATH/post-commit $HOOKS_PATH/old-post-commit;
rm $HOOKS_PATH/post-commit
touch $HOOKS_PATH/post-commit;
chmod +x $HOOKS_PATH/post-commit;
echo '#!/usr/bin/env sh' >> $HOOKS_PATH/post-commit;
echo 'GIT_ROOT="$(git rev-parse --show-toplevel)"' >> $HOOKS_PATH/post-commit;
echo '' >> $HOOKS_PATH/post-commit;
echo '$GIT_ROOT/node_modules/.bin/git-blame-ignore-style-formatting-post-commit-hook' >> $HOOKS_PATH/post-commit;
echo '# Directly invoking module is faster than `yarn run git-blame-ignore-style-formatting-post-commit-hook`' >> $HOOKS_PATH/post-commit;
echo "# (which makes sense, because it's skipping yarn\!)" >> $HOOKS_PATH/post-commit;

If you don't already have a .git-blame-ignore-revs, one will be created for you before this script attempts to write to it:

Created empty .git-blame-ignore-revs file, and preinstall script to configure git to use it.

When you make a style: commit, it will now show something like this after you commit:

Adding .git-blame-ignore-revs entry for last commit. Reason: Starts with "style:"

When/if you are rebasing, and need to refresh the sha, you can simply reword your style: commits to re-run the post-commit hook

-pick 7713c93 style: cleanup comments
-pick c2d2cf6 chore(git-blame): Ignore previous style change
+reword 7713c93 style: cleanup comments
+drop c2d2cf6 chore(git-blame): Ignore previous style change