Prototype pre-commit and commit-msg hook scripts

These hooks perform some basic commit-time checks to keep history clean.

commit-msg

+#!/bin/sh
+#
+# Copy or link this file as ".git/hooks/pre-commit".
+
+die() {
+	echo 'commit-msg hook failure' 1>&2
+	echo '-----------------------' 1>&2
+	echo '' 1>&2
+	echo "$@" 1>&2
+	exit 1
+}
+
+#-----------------------------------------------------------------------------
+# Check the commit message layout with a simple state machine.
+
+msg_first() {
+	len=$(echo -n "$line" | wc -c)
+	if test $len -eq 0; then
+		# not yet first line
+		return
+	elif test $len -lt 8; then
+		die 'The first line must be at least 8 characters:
+--------
+'"$line"'
+--------
+'
+	elif test $len -gt 78; then
+		die 'The first line may be at most 78 characters:
+------------------------------------------------------------------------------
+'"$line"'
+------------------------------------------------------------------------------
+'
+	else
+		# first line okay
+		state=second
+	fi
+}
+
+msg_second() {
+	if test "x$line" != "x"; then
+		die 'The second line must be empty:
+'"$line"
+	else
+		state=rest
+	fi
+}
+
+msg_rest() {
+	false
+}
+
+# Pipe commit message into the state machine.
+state=first
+cat "$1" | grep -v '^#' |
+while read line; do
+	msg_$state || break
+done

pre-commit

+#!/bin/sh
+#
+# Copy or link this file as ".git/hooks/pre-commit".
+
+die() {
+	echo 'pre-commit hook failure' 1>&2
+	echo '-----------------------' 1>&2
+	echo '' 1>&2
+	echo "$@" 1>&2
+	exit 1
+}
+
+#-----------------------------------------------------------------------------
+# Check for committer identity.
+git config --get user.name > /dev/null &&
+git config --get user.email > /dev/null ||
+die 'Identity not configured!  Use the commands
+
+	git config --global user.name '\''Your Name'\''
+	git config --global user.email '\''you@yourdomain.com'\''
+
+to introduce yourself to Git before committing.'
+
+#-----------------------------------------------------------------------------
+# Check content that will be added by this commit.
+
+if git rev-parse --verify -q HEAD > /dev/null; then
+	against=HEAD
+else
+	# Initial commit: diff against an empty tree object
+	against=4b825dc642cb6eb9a060e54bf8d69288fbee4904
+fi
+
+# Disallow non-ascii file names.  The printable range starts at the
+# space character and ends with tilde.
+if test "$(git diff --cached --name-only --diff-filter=A -z $against |
+	   LC_ALL=C tr -d '[ -~]\0')"; then
+	die 'Non-ascii file names may not be added:
+'"$(git diff --cached --name-only --diff-filter=A $against)"
+fi
+
+# Builtin whitespace checks.
+bad=$(git diff-index --check --cached $against --) || die "$bad"