fix: shellcheck precommit

hooks/shellcheck.sh

@@ -1,7 +1,14 @@
 #!/bin/bash
 
+issues=0
+
 for script in "$@"; do
     /usr/bin/shellcheck --exclude=SC2317 --color=always --shell=bash -x --source-path=SCRIPTDIR "$script"
+    [ $? -eq 0 ] || issues=$(($issues + 1))
 done
 
+if [ "$issues" -gt 0 ]; then
+    exit 1
+else
     exit 0
+fi