Fix e2e test conflict scenario and improve action debugging (#6)

* Fix e2e test conflict scenario and improve action debugging

- Expand test file from 3 to 7 lines to avoid git treating adjacent
  line changes as overlapping hunks (was causing spurious conflicts)
- Use line 7 instead of line 3 for conflict test (more separation)
- Fix $CHILD -> $BRANCH typo in conflict resolution instructions
- Add explicit branch parameter to gh pr comment/edit commands
- Add pipefail to catch pipeline failures
- Wrap git merge --abort and gh commands in log_cmd for visibility
- Add debug output at script start for troubleshooting

* Fix e2e test failures and action bugs

Test fixes:
- Expand test file from 3 to 7 lines to avoid git's adjacent-line
  conflict heuristic causing spurious merge conflicts
- Use line 7 instead of line 3 for conflict scenario testing
- Fix conflict resolution: use deterministic file creation instead
  of buggy sed-based conflict marker removal
- Add PRESERVE_ON_FAILURE option for debugging failed tests
- Use fail_test() wrapper for proper cleanup flag handling

Action fixes:
- Fix $CHILD -> $BRANCH typo in conflict resolution instructions
- Add explicit branch parameter to gh pr comment/edit commands
  to ensure they work correctly in GitHub Actions context
- Create autorestack-needs-conflict-resolution label before adding
  it to PR (gh pr edit --add-label fails if label doesn't exist)
- Add pipefail to catch pipeline failures
- Wrap git merge --abort and gh commands in log_cmd for visibility

* Refactor e2e test script

- Remove fail_test helper and TEST_FAILED mechanism since the script
  uses 'set -e', so failures exit automatically. Use exit code in
  cleanup trap instead.
- Replace hardcoded conflict resolution with 'git checkout --ours'
  which correctly preserves feature3's changes to both line 2 and
  line 7
- Remove redundant 'git pull origin main' commands since we use
  'origin/main' references directly and don't need local main updated

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: Phlogistique

tests/test_e2e.sh

@@ -29,6 +29,15 @@ WORKFLOW_FILE="update-pr-stack.yml"
 
 # --- Helper Functions ---
 cleanup() {
+  local exit_code=$?
+  # If PRESERVE_ON_FAILURE is set and there was an error, skip cleanup
+  if [[ "${PRESERVE_ON_FAILURE:-}" == "1" ]] && [[ $exit_code -ne 0 ]]; then
+    echo >&2 "--- Preserving repo for debugging (PRESERVE_ON_FAILURE=1) ---"
+    echo >&2 "Repo: $REPO_FULL_NAME"
+    echo >&2 "Local dir: $TEST_DIR"
+    return 0
+  fi
+
   echo >&2 "--- Cleaning up ---"
   if [[ -d "$TEST_DIR" ]]; then
     echo >&2 "Removing local test directory: $TEST_DIR"
@@ -51,6 +60,7 @@ cleanup() {
 # Trap EXIT signal to ensure cleanup runs even if the script fails
 trap cleanup EXIT
 
+
 # Merge a PR with retry logic to handle transient "not mergeable" errors.
 # After pushing to a PR's base branch, GitHub's mergeability computation is async
 # and can take several seconds. During this time, merge attempts fail with
@@ -196,10 +206,15 @@ log_cmd git init -b main
 log_cmd git config user.email "test-e2e@example.com"
 log_cmd git config user.name "E2E Test Bot"
 
-# Create initial content
+# Create initial content with enough lines for context separation
+# (Git needs ~3 lines of context between changes to avoid treating them as overlapping hunks)
 echo "Base file content line 1" > file.txt
 echo "Base file content line 2" >> file.txt
 echo "Base file content line 3" >> file.txt
+echo "Base file content line 4" >> file.txt
+echo "Base file content line 5" >> file.txt
+echo "Base file content line 6" >> file.txt
+echo "Base file content line 7" >> file.txt
 log_cmd git add file.txt
 log_cmd git commit -m "Initial commit"
 INITIAL_COMMIT_SHA=$(git rev-parse HEAD)
@@ -337,8 +352,6 @@ else
 fi
 # Verify local branches are updated to include the squash commit
 echo >&2 "Checking if branches incorporate the squash commit..."
-log_cmd git checkout main # Ensure main is up-to-date locally
-log_cmd git pull origin main
 log_cmd git checkout feature2 # Checkout local branch first
 log_cmd git pull origin feature2 # Pull updates pushed by the action
 log_cmd git checkout feature3
@@ -398,18 +411,18 @@ echo >&2 "--- Testing Conflict Scenario (Merging PR2) ---"
 
 # 8. Introduce conflicting changes
 echo >&2 "8. Introducing conflicting changes..."
-# Change line 3 on feature3
+# Change line 7 on feature3 (far from line 2 to avoid adjacent-line conflicts)
 log_cmd git checkout feature3
-sed -i '3s/.*/Feature 3 conflicting change line 3/' file.txt
+sed -i '7s/.*/Feature 3 conflicting change line 7/' file.txt
 log_cmd git add file.txt
-log_cmd git commit -m "Conflict: Modify line 3 on feature3"
+log_cmd git commit -m "Conflict: Modify line 7 on feature3"
 FEATURE3_CONFLICT_COMMIT_SHA=$(git rev-parse HEAD) # Store this SHA
 log_cmd git push origin feature3
-# Change line 3 on main
+# Change line 7 on main differently - this will conflict when rebasing feature3 after PR2 merge
 log_cmd git checkout main
-sed -i '3s/.*/Main conflicting change line 3/' file.txt
+sed -i '7s/.*/Main conflicting change line 7/' file.txt
 log_cmd git add file.txt
-log_cmd git commit -m "Conflict: Modify line 3 on main"
+log_cmd git commit -m "Conflict: Modify line 7 on main"
 log_cmd git push origin main
 
 # 9. Trigger Action by Squash Merging PR2 (which is now based on the updated main from step 7)
@@ -501,9 +514,6 @@ echo >&2 "12. Resolving conflict manually on feature3..."
 log_cmd git checkout feature3
 # Ensure we have the latest main which includes the PR2 merge commit AND the conflicting change on main
 log_cmd git fetch origin
-log_cmd git checkout main
-log_cmd git pull origin main # Make sure local main is up-to-date
-log_cmd git checkout feature3
 # Now, perform the merge that the action tried and failed
 echo >&2 "Attempting merge of origin/main into feature3..."
 if git merge origin/main; then
@@ -515,11 +525,9 @@ else
     echo >&2 "Merge conflict occurred as expected. Resolving..."
     # Check status to confirm conflict
     log_cmd git status
-    # Resolve conflict - let's keep the change from feature3 ("Feature 3 conflicting change line 3")
-    # Remove conflict markers and keep the desired line 3
-    sed -i '/<<<<<<< HEAD/,/=======/{//!d}' file.txt # Remove lines between <<<< and ==== (inclusive of <<<<)
-    sed -i '/=======/,/>>>>>>> origin\/main/d' file.txt # Remove lines between ==== and >>>> (inclusive of ==== and >>>>)
-
+    # Resolve conflict - keep feature3's version (ours) of the conflicting file
+    # This preserves both line 2 (Feature 3 content) and line 7 (Feature 3 conflicting change)
+    log_cmd git checkout --ours file.txt
     echo "Resolved file.txt content:"
     cat file.txt
     log_cmd git add file.txt
@@ -534,8 +542,6 @@ echo >&2 "Pushed resolved feature3."
 echo >&2 "13. Verifying conflict resolution..."
 # Fetch the latest state again
 log_cmd git fetch origin
-log_cmd git checkout main
-log_cmd git pull origin main
 log_cmd git checkout feature3
 log_cmd git pull origin feature3
 
@@ -551,25 +557,25 @@ fi
 # Verify the final content of file.txt on feature3
 # Line 1: Original base
 # Line 2: From feature 3 commit ("Feature 3 content line 2")
-# Line 3: From feature 3 conflict commit, kept during resolution ("Feature 3 conflicting change line 3")
+# Line 7: From feature 3 conflict commit, kept during resolution ("Feature 3 conflicting change line 7")
 EXPECTED_CONTENT_LINE1="Base file content line 1"
 EXPECTED_CONTENT_LINE2="Feature 3 content line 2"
-EXPECTED_CONTENT_LINE3="Feature 3 conflicting change line 3"
+EXPECTED_CONTENT_LINE7="Feature 3 conflicting change line 7"
 
 ACTUAL_CONTENT_LINE1=$(sed -n '1p' file.txt)
 ACTUAL_CONTENT_LINE2=$(sed -n '2p' file.txt)
-ACTUAL_CONTENT_LINE3=$(sed -n '3p' file.txt)
+ACTUAL_CONTENT_LINE7=$(sed -n '7p' file.txt)
 
 if [[ "$ACTUAL_CONTENT_LINE1" == "$EXPECTED_CONTENT_LINE1" && \
       "$ACTUAL_CONTENT_LINE2" == "$EXPECTED_CONTENT_LINE2" && \
-      "$ACTUAL_CONTENT_LINE3" == "$EXPECTED_CONTENT_LINE3" ]]; then
+      "$ACTUAL_CONTENT_LINE7" == "$EXPECTED_CONTENT_LINE7" ]]; then
     echo >&2 "✅ Verification Passed: file.txt content on resolved feature3 is correct."
 else
     echo >&2 "❌ Verification Failed: file.txt content on resolved feature3 is incorrect."
     echo "Expected:"
     echo "$EXPECTED_CONTENT_LINE1"
     echo "$EXPECTED_CONTENT_LINE2"
-    echo "$EXPECTED_CONTENT_LINE3"
+    echo "$EXPECTED_CONTENT_LINE7"
     echo "Actual:"
     cat file.txt
     exit 1

update-pr-stack.sh

@@ -7,7 +7,7 @@
 # MERGED_BRANCH - The name of the branch that was merged and will be deleted
 # TARGET_BRANCH - The name of the branch that the PR was merged into
 
-set -ue  # Exit immediately if a command exits with a non-zero status.
+set -ueo pipefail  # Exit on error, undefined var, or pipeline failure
 
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 source "$SCRIPT_DIR/command_utils.sh"
@@ -60,11 +60,11 @@ update_direct_target() {
     log_cmd git update-ref BEFORE_MERGE HEAD
     if ! log_cmd git merge --no-edit "origin/$MERGED_BRANCH"; then
         CONFLICTS+=("origin/$MERGED_BRANCH")
-        git merge --abort
+        log_cmd git merge --abort
     fi
     if ! log_cmd git merge --no-edit SQUASH_COMMIT~; then
         CONFLICTS+=( "$(git rev-parse SQUASH_COMMIT~)" )
-        git merge --abort
+        log_cmd git merge --abort
     fi
 
     if [[ "${#CONFLICTS[@]}" -gt 0 ]]; then
@@ -79,7 +79,7 @@ update_direct_target() {
             echo "#### How to resolve"
             echo '```bash'
             echo "git fetch origin"
-            echo "git switch $CHILD"
+            echo "git switch $BRANCH"
             for conflict in "${CONFLICTS[@]}"; do
                 echo "git merge $conflict"
                 echo "# ..."
@@ -89,8 +89,10 @@ update_direct_target() {
             done
             echo "git push"
             echo '```'
-        } | gh pr comment -F -
-        gh pr edit --add-label autorestack-needs-conflict-resolution
+        } | log_cmd gh pr comment "$BRANCH" -F -
+        # Create the label if it doesn't exist, then add it to the PR
+        gh label create autorestack-needs-conflict-resolution --description "PR needs manual conflict resolution" --color "d73a4a" 2>/dev/null || true
+        log_cmd gh pr edit "$BRANCH" --add-label autorestack-needs-conflict-resolution
     else
         log_cmd git merge --no-edit -s ours "$SQUASH_COMMIT"
         log_cmd git update-ref MERGE_RESULT "HEAD^{tree}"