Fix problem that pre_commit_hook passes multiple args as single arg

-  not to use `readarray` built-in func (consider bash 3.x)

git-secrets

@@ -169,11 +169,13 @@ commit_msg_hook() {
 # Scans all files that are about to be committed.
 pre_commit_hook() {
   SCAN_CACHED=1
-  local file found_match=0 rev="4b825dc642cb6eb9a060e54bf8d69288fbee4904"
+  local files=() file found_match=0 rev="4b825dc642cb6eb9a060e54bf8d69288fbee4904"
   # Diff against HEAD if this is not the first commit in the repo.
   git rev-parse --verify HEAD >/dev/null 2>&1 && rev="HEAD"
   # Filter out deleted files using --diff-filter
-  readarray -t files <<< $(git diff-index --diff-filter 'ACMU' --name-only --cached $rev --)
+  while IFS= read -r file; do
+    files+=("$file")
+  done <<< "$(git diff-index --diff-filter 'ACMU' --name-only --cached $rev --)"
   scan_with_fn_or_die "scan" "${files[@]}"
 }