chore: add a pre-commit hook to auto format erlang code

.gitattributes

@@ -7,3 +7,4 @@ scripts/* text eol=lf
 *.jpg -text
 *.png -text
 *.pdf -text
+scripts/erlfmt -text

scripts/git-hook-pre-commit.sh

@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+files="$(git diff --cached --name-only | grep -E '.*\.erl' || true)"
+if [[ "${files}" == '' ]]; then
+    exit 0
+fi
+files="$(echo -e "$files" | xargs)"
+# shellcheck disable=SC2086
+./scripts/erlfmt -c $files

scripts/git-hooks-init.sh

@@ -11,3 +11,7 @@ mkdir -p ".git/hooks"
 if [ ! -L '.git/hooks/pre-push' ]; then
     ln -sf '../../scripts/git-hook-pre-push.sh' '.git/hooks/pre-push'
 fi
+
+if [ ! -L '.git/hooks/pre-commit' ]; then
+    ln -sf '../../scripts/git-hook-pre-commit.sh' '.git/hooks/pre-commit'
+fi