Update diff-sha.sh

diff-sha.sh

@@ -220,21 +220,23 @@ else
         depth=$INPUT_FETCH_DEPTH
         max_depth=$INPUT_MAX_FETCH_DEPTH
 
-        while ! git diff --name-only --ignore-submodules=all "$PREVIOUS_SHA$DIFF$CURRENT_SHA" 1>/dev/null 2>&1; do
+        for ((i=0; i<max_depth; i+=depth)); do
           echo "Fetching $depth commits..."
 
           # shellcheck disable=SC2086
           git fetch $EXTRA_ARGS -u --progress --deepen="$depth" origin +"$GITHUB_REF":refs/remotes/origin/"$CURRENT_BRANCH"
 
           PREVIOUS_SHA=$(git merge-base "$TARGET_BRANCH" "$CURRENT_SHA" 2>&1) && exit_status=$? || exit_status=$?
 
-          if [[ $depth -gt $max_depth ]]; then
-            echo "::error::Unable to locate a common ancestor between $TARGET_BRANCH and $CURRENT_SHA"
-            exit 1
+          if git diff --name-only --ignore-submodules=all "$PREVIOUS_SHA$DIFF$CURRENT_SHA" 1>/dev/null 2>&1; then
+            break
           fi
-
-          depth=$((depth + 300))
         done
+
+        if ((i >= max_depth)); then
+          echo "::error::Unable to locate a common ancestor between $TARGET_BRANCH and $CURRENT_SHA"
+          exit 1
+        fi
       else
         echo "::debug::Not a shallow clone, skipping merge-base check."
       fi