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Fix stuck PRs from incomplete conflict-resolution comment
When updating a descendant branch after its parent PR was squash-merged hits a merge conflict, the bot posts a comment telling the author how to finish by hand. That comment listed only the ref that conflicted, so a human following it ran a single `git merge` and ended up with a branch still missing the parent-branch merge and the `-s ours` squash record — never mergeable into its new base, so it stayed stuck. The sequence is the same whichever merge conflicts, so the comment now prints it in full: merge the parent branch, merge the pre-squash target, then record the squash with `-s ours`. This fixes the comment only; the author runs the steps by hand. Diagnosed on sensei #7987. Adds an offline regression test that replays the comment's commands and asserts the branch ends up mergeable. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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‎tests/test_conflict_comment_completeness.sh‎

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#!/bin/bash
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#
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# Regression test for the conflict-resolution comment.
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#
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# THE BUG:
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# update_direct_target() merges several refs into a descendant branch:
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# 1. origin/$MERGED_BRANCH (the parent PR's tip)
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# 2. $SQUASH_COMMIT~ (the target branch just before the squash)
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# 3. -s ours $SQUASH_COMMIT (record the squash as merged, keep the tree)
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# When merge #1 is clean but merge #2 conflicts, only the conflicting ref used
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# to be listed in the "How to resolve" steps. A human following the comment
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# literally would merge ONLY $SQUASH_COMMIT~, ending up with a branch that is
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# missing both the parent's content (merge #1) and the squash ancestry (#3).
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# Such a branch is not cleanly mergeable into its new base, so the
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# synchronize-triggered continuation never makes progress and the label stays
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# stuck on the PR.
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#
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# This test reproduces exactly that topology, replays the merge commands the
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# comment tells the human to run, and asserts the branch ends up mergeable
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# (squash commit and parent content are both present).
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#
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# It runs fully offline using mock gh/git, like the other unit tests.
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set -e
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SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
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source "$SCRIPT_DIR/../command_utils.sh"
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simulate_push() {
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log_cmd git update-ref "refs/remotes/origin/$1" "$1"
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}
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TEST_REPO=$(mktemp -d)
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cd "$TEST_REPO"
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echo "Created test repo at $TEST_REPO"
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# A mock gh that records the conflict comment and otherwise stays quiet.
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COMMENT_FILE="$TEST_REPO/conflict_comment.md"
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cat > "$TEST_REPO/mock_gh.sh" <<MOCK
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#!/bin/bash
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if [[ "\$1" == "pr" && "\$2" == "list" ]]; then
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# Only feature2 is a direct child of feature1 in this scenario.
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base=""
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for ((i=1; i<=\$#; i++)); do
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if [[ "\${!i}" == "--base" ]]; then next=\$((i+1)); base="\${!next}"; fi
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done
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[[ "\$base" == "feature1" ]] && echo "feature2"
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elif [[ "\$1" == "pr" && "\$2" == "comment" ]]; then
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cat > "$COMMENT_FILE"
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elif [[ "\$1" == "label" || ( "\$1" == "pr" && "\$2" == "edit" ) ]]; then
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: # ignore label creation / edits
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else
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echo "Unknown gh command: \$@" >&2
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exit 1
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fi
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MOCK
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chmod +x "$TEST_REPO/mock_gh.sh"
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# Replaying merges may create non-ff merge commits; never open an editor.
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export GIT_EDITOR=true
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log_cmd git init -b main
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log_cmd git config user.email "test@example.com"
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log_cmd git config user.name "Test User"
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# 12-line file so changes on different lines do not collide.
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for i in $(seq 1 12); do echo "line $i" >> file.txt; done
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log_cmd git add file.txt
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log_cmd git commit -m "Initial commit"
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simulate_push main
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# feature1 (the parent PR): first commit on line 2.
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log_cmd git checkout -b feature1
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sed -i '2s/.*/f1 commit 1/' file.txt
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log_cmd git add file.txt
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log_cmd git commit -m "f1: commit 1"
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simulate_push feature1
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# feature2 (the child PR): branched off feature1, changes line 9.
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log_cmd git checkout -b feature2
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sed -i '9s/.*/f2 content line 9/' file.txt
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log_cmd git add file.txt
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log_cmd git commit -m "f2: change line 9"
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simulate_push feature2
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# feature1 advances AFTER feature2 branched (line 4). feature2 never picks
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# this up, so merging origin/feature1 into feature2 is clean and substantive.
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log_cmd git checkout feature1
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sed -i '4s/.*/f1 commit 2/' file.txt
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log_cmd git add file.txt
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log_cmd git commit -m "f1: commit 2"
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simulate_push feature1
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# main advances on line 9 with content that conflicts with feature2.
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log_cmd git checkout main
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sed -i '9s/.*/main conflicting line 9/' file.txt
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log_cmd git add file.txt
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log_cmd git commit -m "main: conflicting change on line 9"
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simulate_push main
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# Squash-merge feature1 into main. SQUASH_COMMIT~ is now main carrying the
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# conflicting line-9 change; merging it into feature2 conflicts.
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log_cmd git checkout main
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log_cmd git merge --squash feature1
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log_cmd git commit -m "Squash merge feature1"
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SQUASH_COMMIT=$(git rev-parse HEAD)
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simulate_push main
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echo "Squash commit: $SQUASH_COMMIT"
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echo ""
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echo "=== Graph before running the action ==="
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log_cmd git log --graph --oneline --all
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echo ""
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# Run the action. We expect a conflict and a posted comment (exit 1 from
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# update_direct_target is swallowed by main, which returns 0).
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log_cmd \
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env \
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SQUASH_COMMIT="$SQUASH_COMMIT" \
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MERGED_BRANCH=feature1 \
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TARGET_BRANCH=main \
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GH="$TEST_REPO/mock_gh.sh" \
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GIT="$SCRIPT_DIR/mock_git.sh" \
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"$SCRIPT_DIR/../update-pr-stack.sh"
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if [[ ! -f "$COMMENT_FILE" ]]; then
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echo "❌ No conflict comment was posted; scenario did not trigger a conflict"
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exit 1
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fi
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echo ""
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echo "=== Conflict comment posted to the PR ==="
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cat "$COMMENT_FILE"
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echo ""
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# Simulate the human doing EXACTLY what the comment says: start from the
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# branch as it exists on the remote (the action never pushes its local merge),
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# then run each `git merge` line, resolving any conflict by keeping our side.
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log_cmd git checkout feature2
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log_cmd git reset --hard origin/feature2
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MERGE_CMDS=$(grep -E '^git merge' "$COMMENT_FILE" || true)
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if [[ -z "$MERGE_CMDS" ]]; then
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echo "❌ Comment lists no 'git merge' commands to follow"
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exit 1
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fi
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while IFS= read -r cmd; do
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echo "Human runs: $cmd"
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if ! log_cmd bash -c "$cmd"; then
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echo "Resolving conflict by keeping our (feature2) side..."
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log_cmd git checkout --ours -- file.txt
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log_cmd git add file.txt
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log_cmd git commit --no-edit
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fi
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done <<< "$MERGE_CMDS"
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simulate_push feature2
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echo ""
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echo "=== feature2 after following the comment ==="
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log_cmd git log --graph --oneline --all
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echo ""
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# After following the comment, the branch must be cleanly mergeable into its
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# new base (main). That requires the squash commit to be an ancestor (so the
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# diff against main is clean) and the parent's advanced content to be present.
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FAILED=0
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if log_cmd git merge-base --is-ancestor "$SQUASH_COMMIT" feature2; then
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echo "✅ feature2 includes the squash commit (mergeable into main)"
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else
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echo "❌ BUG: feature2 is missing the squash commit after following the comment."
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echo " The PR cannot be cleanly merged into its new base; the continuation"
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echo " workflow will never make progress and the conflict label stays stuck."
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FAILED=1
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fi
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if log_cmd git merge-base --is-ancestor origin/feature1 feature2; then
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echo "✅ feature2 includes the parent branch's advanced content"
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else
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echo "❌ BUG: feature2 is missing origin/feature1's content (merge #1 was"
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echo " omitted from the comment)."
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FAILED=1
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fi
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if [[ "$FAILED" -ne 0 ]]; then
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exit 1
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fi
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echo ""
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echo "All conflict-comment-completeness tests passed! 🎉"
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echo "Test repository remains at: $TEST_REPO for inspection"

‎update-pr-stack.sh‎

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Original file line numberDiff line numberDiff line change
@@ -45,17 +45,6 @@ has_squash_commit() {
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&& git merge-base --is-ancestor SQUASH_COMMIT "$BRANCH"
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}
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format_branch_list_for_text() {
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for ((i=1; i<=$#; i++)); do
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case $i in
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1) format='`%s`';;
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$#) format=', and `%s`';;
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*) format=', `%s`';;
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esac
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printf "$format" "${!i}"
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done
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}
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update_direct_target() {
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local BRANCH="$1"
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local BASE_BRANCH="$2"
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{
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echo "### ⚠️ Automatic update blocked by merge conflicts"
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echo
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echo -n "I tried to merge "
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format_branch_list_for_text "${CONFLICTS[@]}"
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echo " into this branch while updating the pull request stack and hit conflicts."
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echo "I hit a merge conflict while updating this pull request after its base branch was squash-merged. Please resolve it by hand by running these in order:"
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echo
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echo "#### How to resolve"
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echo '```bash'
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echo "git fetch origin"
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echo "git switch $BRANCH"
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for conflict in "${CONFLICTS[@]}"; do
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echo "git merge $conflict"
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echo "# ..."
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echo '# fix conflicts, for instance with `git mergetool`'
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echo "# ..."
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echo "git commit"
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done
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echo "git merge origin/$MERGED_BRANCH"
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echo "git merge $(git rev-parse SQUASH_COMMIT~)"
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echo "# record the squash commit as merged without re-applying its changes:"
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echo "git merge -s ours $(git rev-parse SQUASH_COMMIT)"
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echo "git push"
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echo '```'
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echo
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echo 'If a merge stops with conflicts, fix them (for instance with `git mergetool`), `git commit`, then run the next command.'
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echo
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echo "Once you push, this action will resume and finish updating this pull request."
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} | log_cmd gh pr comment "$BRANCH" -F -
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# Create the label if it doesn't exist, then add it to the PR

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