feat: add parallel execution with -j/--jobs flag

- Add -j/--jobs N flag to run N commits in parallel
- Use xargs -P for reliable parallel execution
- Refactor to use process_commit wrapper function
- Falls back to sequential when -j 1 or not specified
- Should provide 3-4x speedup when checking multiple commits

check-history.sh

@@ -2,21 +2,51 @@
 set -euo pipefail
 
 # Usage:
-#   check-history.sh <start_offset> <count> [--verbose]
+#   check-history.sh <start_offset> <count> [OPTIONS]
 # Example:
 #   check-history.sh 2 4         # checks commits 2,3,4,5
-#   check-history.sh 5 1   # checks only commit 5
+#   check-history.sh 5 1 -v      # verbose mode
-#   check-history.sh 1 1 --verbose   # verbose mode
+#   check-history.sh 2 28 -j4    # check 28 commits, 4 at a time
 
 VERBOSE=0
-if [ $# -lt 2 ] || [ $# -gt 3 ]; then
+JOBS=1
-    echo "Usage: $0 <start_offset_from_head> <count> [--verbose|-v]"
+
+# Parse arguments
+if [ $# -lt 2 ]; then
+    echo "Usage: $0 <start_offset_from_head> <count> [--verbose|-v] [-j|--jobs N]"
     exit 1
 fi
 
-if [ $# -eq 3 ] && { [ "$3" = "--verbose" ] || [ "$3" = "-v" ]; }; then
+START_ARG="$1"
+COUNT_ARG="$2"
+shift 2
+
+# Parse optional flags
+while [ $# -gt 0 ]; do
+    case "$1" in
+        -v|--verbose)
             VERBOSE=1
-fi
+            shift
+            ;;
+        -j|--jobs)
+            if [ $# -lt 2 ]; then
+                echo "Error: -j/--jobs requires a number" >&2
+                exit 1
+            fi
+            JOBS="$2"
+            if ! [[ "$JOBS" =~ ^[0-9]+$ ]] || [ "$JOBS" -lt 1 ]; then
+                echo "Error: -j/--jobs must be a positive integer" >&2
+                exit 1
+            fi
+            shift 2
+            ;;
+        *)
+            echo "Error: Unknown option $1" >&2
+            echo "Usage: $0 <start_offset_from_head> <count> [--verbose|-v] [-j|--jobs N]"
+            exit 1
+            ;;
+    esac
+done
 
 # Debug logging helper
 debug() {
@@ -26,8 +56,8 @@ debug() {
 }
 
 # Convert user-friendly 1-indexed "Nth from HEAD" into 0-indexed offset
-START_OFFSET="$(( $1 - 1 ))"
+START_OFFSET="$(( START_ARG - 1 ))"
-COUNT="$2"
+COUNT="$COUNT_ARG"
 REPO_ROOT="$(git rev-parse --show-toplevel)"
 TMP_BASE="/tmp/check-history-$$"
 WORKTREES_DIR="$TMP_BASE/worktrees"
@@ -40,7 +70,11 @@ debug "PNPM_STORE: $PNPM_STORE"
 
 mkdir -p "$WORKTREES_DIR" "$LOGS_DIR" "$PNPM_STORE"
 
-echo "Checking commits from offset $1 (HEAD~$START_OFFSET) for $COUNT commits…"
+if [ "$JOBS" -gt 1 ]; then
+    echo "Checking commits from offset $START_ARG (HEAD~$START_OFFSET) for $COUNT commits with $JOBS parallel jobs…"
+else
+    echo "Checking commits from offset $START_ARG (HEAD~$START_OFFSET) for $COUNT commits…"
+fi
 echo
 
 # Build list of commits as if by `git rebase -i HEAD~N` (HEAD=0 newest) as if by `git rebase -i HEAD~N`
@@ -153,7 +187,9 @@ build_frontend() {
 # -----------------------------
 cleanup() {
     echo "
-Caught interrupt, cleaning worktrees…" >&2
+Caught interrupt, killing background jobs and cleaning worktrees…" >&2
+    # Kill all background jobs
+    jobs -p | xargs -r kill 2>/dev/null || true
     git worktree prune >/dev/null 2>&1 || true
     rm -rf "$TMP_BASE" >/dev/null 2>&1 || true
     exit 130
@@ -215,36 +251,57 @@ check_commit() {
 }
 
 # -----------------------------
-# Sequential execution
+# Execution (parallel or sequential)
 # -----------------------------
 FAIL=0
-i=1
 TOTAL=${#COMMITS[@]}
-for commit in "${COMMITS[@]}"; do
-    worktree="$WORKTREES_DIR/$commit"
-    log="$LOGS_DIR/$commit.log"
 
-    debug "===== Processing commit $i/$TOTAL ====="
+# Export functions and variables for parallel execution
-    debug "Commit: $commit"
+export -f check_commit build_frontend debug
-    debug "Worktree: $worktree"
+export VERBOSE REPO_ROOT PNPM_STORE WORKTREES_DIR LOGS_DIR
-    debug "Log file: $log"
 
-    echo "[ $i / $TOTAL ] Checking $commit…"
+# Process a single commit (for xargs)
-    if ! check_commit "$commit" "$worktree" "$log"; then
+process_commit() {
+    local idx="$1"
+    local commit="$2"
+    local worktree="$WORKTREES_DIR/$commit"
+    local log="$LOGS_DIR/$commit.log"
+
+    echo "[ $((idx + 1)) / $TOTAL ] Checking $commit…"
+
+    if check_commit "$commit" "$worktree" "$log"; then
+        echo "✓ [ $((idx + 1)) / $TOTAL ] $commit passed"
+        sed 's/^/    /' "$log"
+        git worktree remove --force "$worktree" >/dev/null 2>&1 || true
+        echo
+        return 0
+    else
         echo "❌ FAILED at commit $commit"
         sed 's/^/    /' "$log"
+        echo
+        return 1
+    fi
+}
+export -f process_commit
+export TOTAL
+
+if [ "$JOBS" -eq 1 ]; then
+    # Sequential execution
+    for i in "${!COMMITS[@]}"; do
+        if ! process_commit "$i" "${COMMITS[$i]}"; then
             FAIL=1
             break
         fi
-    debug "Commit $commit passed"
+    done
-    sed 's/^/    /' "$log"
+else
+    # Parallel execution using xargs
+    debug "Starting parallel execution with $JOBS jobs"
 
-    debug "Removing worktree at $worktree"
+    # Create input for xargs: "index commit"
-    git worktree remove --force "$worktree" >/dev/null 2>&1
+    for i in "${!COMMITS[@]}"; do
-
+        echo "$i ${COMMITS[$i]}"
-    ((i++))
+    done | xargs -P "$JOBS" -n 2 bash -c 'process_commit "$@"' _ || FAIL=1
-    echo
+fi
-done
 
 # -----------------------------
 # Final output