Adds pre-commit hook that runs automated tests & fixes lint errors

.githooks/pre-commit

@@ -0,0 +1,62 @@
+#!/bin/sh
+
+# Setup for the check for filenames with non-ASCII characters
+if git rev-parse --verify HEAD >/dev/null 2>&1
+then
+	against=HEAD
+else
+	# Initial commit: diff against an empty tree object
+	against=$(git hash-object -t tree /dev/null)
+fi
+
+# If you want to allow non-ASCII filenames set this variable to true.
+allownonascii=$(git config --type=bool hooks.allownonascii)
+
+# Redirect output to stderr.
+exec 1>&2
+
+# Cross platform projects tend to avoid non-ASCII filenames; prevent
+# them from being added to the repository. We exploit the fact that the
+# printable range starts at the space character and ends with tilde.
+if [ "$allownonascii" != "true" ] &&
+	# Note that the use of brackets around a tr range is ok here, (it's
+	# even required, for portability to Solaris 10's /usr/bin/tr), since
+	# the square bracket bytes happen to fall in the designated range.
+	test $(git diff-index --cached --name-only --diff-filter=A -z $against |
+	  LC_ALL=C tr -d '[ -~]\0' | wc -c) != 0
+then
+	cat <<\EOF
+Error: Attempt to add a non-ASCII file name.
+This can cause problems if you want to work with people on other platforms.
+To be portable it is advisable to rename the file.
+If you know what you are doing you can disable this check using:
+  git config hooks.allownonascii true
+EOF
+	exit 1
+fi
+
+# lints changed JavaScript and TypeScript
+changed_js=$(git diff-index --cached --name-only $against | grep -E "(.*\.(js|mjs|ts|mts)|scripts/.*\.(js|mjs|ts|mts)|src/.*\.(js|mjs|ts|mts)|test/.*\.(js|mjs|ts|mts)|admin/.*\.(js|mjs|ts|mts)|admin/src/.*\.(js|mjs|ts|mts))$")
+# /dev/null prevents eslint from checking everything
+./node_modules/.bin/eslint ${changed_js:-/dev/null}
+LINT_STATUS=$?
+if [ "$LINT_STATUS" != "0" ]; then
+  echo 'Fix the errors above, then use `git add` to restage all fixed files'
+  exit $LINT_STATUS
+fi
+
+# lints changed HTML
+changed_html=$(git diff-index --cached --name-only $against | grep -E "^src/.*\.html$")
+# src/tokens.html prevents htmlhint from checking everything
+node_modules/.bin/htmlhint ${changed_html:-src/tokens.html}
+LINT_STATUS=$?
+if [ "$LINT_STATUS" != "0" ]; then
+  echo 'Fix the errors above, then use `git add` to restage all fixed files'
+  exit $LINT_STATUS
+fi
+
+# runs all automated tests
+npm run test:unit
+
+# If there are whitespace errors, print the offending file names and fail.
+exec git diff-index --check --cached $against --

README.md

@@ -45,6 +45,13 @@ Read our [contributor guide](./CONTRIBUTING.md) to learn how you can submit bug
 
 We're also looking for help with localization. The Hubs redesign has a lot of new text and we need help from people like you to translate it. Follow the [localization docs](./src/assets/locales/README.md) to get started.
 
+A Git hook will run before each commit, to lint and test the code.
+Fix the issues it complains about, then the hook will allow your commit.
+The checks are also run in Continuous Integration, so you'll be requested to fix a Pull Request that fails these checks — the Git hook just gives you faster feedback.
+In unusual situations, you can suppress the checks by adding the flag `-n` to your commit command.
+
+To run the checks *before* you commit, run `npm run test`.
+
 Contributors are expected to abide by the project's [Code of Conduct](./CODE_OF_CONDUCT.md) and to be respectful of the project and people working on it.
 
 ## Additional Resources

package.json

@@ -14,6 +14,7 @@
   },
   "scripts": {
     "info": "npm-scripts-info",
+    "dependencies": "git config --local core.hooksPath .githooks/ || true",
     "start": "webpack serve --mode=development --env loadAppConfig=1",
     "dev": "webpack serve --mode=development --env remoteDev=1 --progress",
     "local": "webpack serve --mode=development --env localDev=1",