Add a script for easy execution of diff-only pre-commit checks

bin/pre-commit-diff.sh

+#!/bin/bash
+
+# We'd like to run the pre-commit hooks only on files that are being modified by
+# this merge request, however `CI_MERGE_REQUEST_TARGET_BRANCH_SHA` is a'premium'
+# feature according to GitLab... so this is a workaround for extracting the hash
+CI_MERGE_REQUEST_TARGET_BRANCH_NAME="${1:-master}"  # Set to master or 1st input
+CI_COMMIT_SHA=$(git rev-parse HEAD)
+CI_MERGE_REQUEST_TARGET_BRANCH_SHA=$(git ls-remote origin $CI_MERGE_REQUEST_TARGET_BRANCH_NAME | cut -d$'\t' -f1)
+FILES=$(git diff $CI_COMMIT_SHA  $CI_MERGE_REQUEST_TARGET_BRANCH_SHA --name-only | tr '\n' ' ')
+echo "Running pre-commit on diff from  $CI_COMMIT_SHA to $CI_MERGE_REQUEST_TARGET_BRANCH_SHA ($CI_MERGE_REQUEST_TARGET_BRANCH_NAME)"
+#  Pass list of modified files to pre-commit so that it only checks them
+echo $FILES | xargs pre-commit run --color=always --files