meta:hooks:pre-commit: Check for broken symlinks

Check that added/moved symlinks are not broken.

meta/git/hooks/pre-commit

@@ -44,3 +44,16 @@ fi
 if ! git diff-index --check --cached $against --; then
 	die
 fi
+
+# Check that added symlinks are not broken
+git diff --staged --name-only --diff-filter=AR $against \
+| {
+       broken=0
+       while read -r line; do
+               if [ -h "$line" ] && [ ! -e "$line" ]; then
+                       broken=1
+                       printf "%s\n" "$line: Broken symlink" >&2
+               fi
+       done
+       (( ! broken )) || die
+}