TO-SPLIT

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

.github/workflows/rebase-shears.yml

@@ -87,7 +87,7 @@ jobs:
             exit 0
           fi
           
-          if ./ci/rebase-branch.sh "shears/$BRANCH" "$UPSTREAM" ./ci; then
+          if ./ci/rebase-branch.sh "shears/$BRANCH" "$UPSTREAM" "$PWD/ci"; then
             echo "to_push=shears/$BRANCH" >>"$GITHUB_OUTPUT"
           else
             echo "failed_worktrees=$PWD/rebase-worktree-$BRANCH" >>"$GITHUB_OUTPUT"
@@ -121,7 +121,7 @@ jobs:
             fi
             
             worktree="$PWD/rebase-worktree-$BRANCH"
-            if ./ci/rebase-branch.sh "shears/$BRANCH" "$UPSTREAM" ./ci; then
+            if ./ci/rebase-branch.sh "shears/$BRANCH" "$UPSTREAM" "$PWD/ci"; then
               to_push="${to_push:+$to_push }shears/$BRANCH"
             else
               echo "::error::Rebase failed for shears/$BRANCH"

ci/rebase-branch.sh

@@ -37,24 +37,29 @@ usage () {
 	exit 1
 }
 
-# Function to check if patch was trivially upstreamed (exact range-diff match)
-check_trivial_skip () {
-	# Try range-diff with default creation factor to find exact matches
-	# range-diff may fail if there's no common base, which is fine - just means no trivial match
-	if ! local range_diff_output=$(git range-diff --no-color REBASE_HEAD^! REBASE_HEAD..); then
-		# range-diff failed (no common ancestor, etc.) - not a trivial skip
-		return 1
-	fi
+# Function to generate a correspondence map between two commit ranges
+# Usage: generate_correspondence_map <our-range> <their-range> <output-file>
+# The map file contains range-diff output that can be searched for correspondences
+generate_correspondence_map () {
+	local our_range=$1 their_range=$2 output_file=$3
+	git -c core.abbrev=false range-diff --no-color "$our_range" "$their_range" >"$output_file" 2>/dev/null || :
+}
 
-	# Look for exact match: "1: abc123 = 1: def456"
-	# The "=" means identical patches
-	if echo "$range_diff_output" | grep -qE '^[0-9]+: [0-9a-f]+ = [0-9]+: [0-9a-f]+'; then
-		# Extract the upstream OID (right side of =)
-		echo "$range_diff_output" | grep -oE '^[0-9]+: [0-9a-f]+ = [0-9]+: ([0-9a-f]+)' | \
-			sed 's/.*= [0-9]*: //' | head -1
-		return 0
-	fi
-	return 1
+# Function to find a corresponding commit in a map file
+# Usage: find_correspondence <oid> <map-file>
+# Returns: corresponding OID on stdout, exit 0 if found (= or ! match), 1 if not
+# Sets CORRESPONDENCE_TYPE to "=" (identical) or "!" (modified)
+find_correspondence () {
+	local oid=$1 map_file=$2
+	test -s "$map_file" || return 1
+	
+	# Look for this OID in the left side of range-diff output
+	# Format: "N: <oid> = M: <oid>" (identical) or "N: <oid> ! M: <oid>" (modified)
+	local match=$(sed -n "s/^[0-9]*: $oid \([!=]\) [0-9]*: \([0-9a-f]*\).*/\1 \2/p" "$map_file" | head -1)
+	test -n "$match" || return 1
+	
+	CORRESPONDENCE_TYPE=${match% *}
+	echo "${match#* }"
 }
 
 # Generate git log -L commands for conflicting hunks
@@ -82,7 +87,10 @@ generate_log_l_commands () {
 }
 
 # Function to resolve a single conflict with AI
+# Usage: resolve_conflict_with_ai [<tried-correspondences>]
 resolve_conflict_with_ai () {
+	local tried_correspondences=$1
+	
 	# Get REBASE_HEAD info once
 	local rebase_head_oid rebase_head_ref rebase_head_oneline
 	rebase_head_oid=$(git rev-parse REBASE_HEAD)
@@ -101,11 +109,20 @@ resolve_conflict_with_ai () {
 		log_l_commands="${log_l_commands}$(generate_log_l_commands "$file")"
 	done
 
+	# Add context about tried correspondences
+	local correspondence_context=""
+	if test -n "$tried_correspondences"; then
+		correspondence_context="
+Note: We found corresponding commits from previous/sibling rebases but they did not apply cleanly:
+$tried_correspondences
+You may want to examine these with 'git show <oid>' for hints on how to resolve."
+	fi
+
 	# Build the prompt - minimal, letting LLM discover context
 	local prompt="Resolve merge conflict during rebase of commit REBASE_HEAD.
 
 Conflicting files: $conflicting_files
-
+$correspondence_context
 Investigation commands:
 - See the patch: git show REBASE_HEAD
 - See conflict markers: view <file>
@@ -297,15 +314,16 @@ run_rebase_with_ai () {
 		rebase_head_ref=$(git show --no-patch --format=reference REBASE_HEAD)
 		rebase_head_oneline=$(git show --no-patch --format='%h %s' REBASE_HEAD)
 
-		# First, try trivial skip check (exact range-diff match)
-		if local trivial_upstream_oid=$(check_trivial_skip); then
-			echo "$rebase_head_oid $trivial_upstream_oid" >>"$SKIPPED_MAP_FILE"
-			echo "::notice::Trivial skip (upstream: $trivial_upstream_oid): $rebase_head_oneline"
+		# Check upstream correspondence (= means identical, skip it)
+		if corresponding_oid=$(find_correspondence "$rebase_head_oid" "$UPSTREAM_MAP") &&
+		   test "$CORRESPONDENCE_TYPE" = "="; then
+			echo "$rebase_head_oid $corresponding_oid" >>"$SKIPPED_MAP_FILE"
+			echo "::notice::Trivial skip (upstream: $corresponding_oid): $rebase_head_oneline"
 			cat >>"$REPORT_FILE" <<TRIVIAL_SKIP_EOF
 
 ### Skipped (trivial): $rebase_head_ref
 
-Upstream equivalent: $(git show --no-patch --format=reference "$trivial_upstream_oid" || echo "$trivial_upstream_oid")
+Upstream equivalent: $(git show --no-patch --format=reference "$corresponding_oid" 2>/dev/null || echo "$corresponding_oid")
 
 Detected via exact range-diff match (no AI needed).
 
@@ -315,8 +333,34 @@ TRIVIAL_SKIP_EOF
 			continue
 		fi
 
-		# Non-trivial conflict - invoke AI
-		resolve_conflict_with_ai
+		# Try previous/sibling correspondences (reuse their resolution via merge-tree)
+		local tried_correspondences=""
+		for map_file in "$PREVIOUS_MAP" "$SIBLING_MAP"; do
+			test -s "$map_file" || continue
+			corresponding_oid=$(find_correspondence "$rebase_head_oid" "$map_file") || continue
+			
+			echo "::notice::Found correspondence: $corresponding_oid for $rebase_head_oneline"
+			tried_correspondences="${tried_correspondences:+$tried_correspondences }$corresponding_oid"
+			# Try merge-tree: if clean, use the resulting tree
+			if result_tree=$(git merge-tree --write-tree HEAD^ REBASE_HEAD "$corresponding_oid" 2>/dev/null) &&
+			   git read-tree --reset -u "$result_tree" &&
+			   git commit -C REBASE_HEAD; then
+				echo "::notice::Used resolution from: $corresponding_oid"
+				cat >>"$REPORT_FILE" <<RESOLVED_EOF
+
+### Resolved via correspondence: $rebase_head_ref
+
+Used resolution from: $(git show --no-patch --format=reference "$corresponding_oid" 2>/dev/null || echo "$corresponding_oid")
+
+RESOLVED_EOF
+				CONFLICTS_RESOLVED=$((CONFLICTS_RESOLVED + 1))
+				git rebase --continue
+				continue 2
+			fi
+		done
+
+		# Non-trivial conflict - invoke AI (pass tried correspondences as context)
+		resolve_conflict_with_ai "$tried_correspondences"
 	done
 }
 
@@ -369,14 +413,28 @@ echo "::notice::Current tip: $TIP_OID"
 # The second parent of the marker points to the GfW branch tip at marker creation time
 GFW_MAIN_BRANCH="origin/main"
 BEHIND_COUNT=$(git rev-list --count "$TIP_OID..$GFW_MAIN_BRANCH" || echo "0")
+PREVIOUS_MAP=""
 
 if test "$BEHIND_COUNT" -gt 0; then
-	echo "::notice::Syncing $BEHIND_COUNT commits from $GFW_MAIN_BRANCH"
-	echo "::group::Sync rebase from $GFW_MAIN_BRANCH"
-	run_rebase_with_ai -r HEAD "$GFW_MAIN_BRANCH"
-	git checkout -B "$SHEARS_BRANCH"
-	TIP_OID=$(git rev-parse HEAD)
-	echo "::endgroup::"
+	if git rev-list --grep='^Start the merging-rebase' "$TIP_OID..$GFW_MAIN_BRANCH" | grep -q .; then
+		# origin/main was rebased - generate correspondence before adopting
+		PREVIOUS_MAP="$WORKTREE_DIR/previous-correspondence.map"
+		MAIN_MARKER=$(git rev-parse "$GFW_MAIN_BRANCH^{/Start.the.merging-rebase}")
+		generate_correspondence_map "$MAIN_MARKER..$GFW_MAIN_BRANCH" "$OLD_MARKER..$TIP_OID" "$PREVIOUS_MAP"
+		
+		echo "::notice::origin/main was rebased, adopting its $BEHIND_COUNT commits"
+		git checkout -B "$SHEARS_BRANCH" "$GFW_MAIN_BRANCH"
+		TIP_OID=$(git rev-parse HEAD)
+		OLD_MARKER=$(git rev-parse "HEAD^{/Start.the.merging-rebase}")
+		OLD_UPSTREAM=$(git rev-parse "$OLD_MARKER^1")
+	else
+		echo "::notice::Syncing $BEHIND_COUNT commits from $GFW_MAIN_BRANCH"
+		echo "::group::Rebasing $BEHIND_COUNT commits from $GFW_MAIN_BRANCH on top of $SHEARS_BRANCH"
+		run_rebase_with_ai -r HEAD "$GFW_MAIN_BRANCH"
+		git checkout -B "$SHEARS_BRANCH"
+		TIP_OID=$(git rev-parse HEAD)
+		echo "::endgroup::"
+	fi
 fi
 
 # Initialize report
@@ -396,21 +454,41 @@ CONFLICTS_RESOLVED=0
 SKIPPED_MAP_FILE="$WORKTREE_DIR/skipped-commits.map"
 : >"$SKIPPED_MAP_FILE"
 
-# Create new marker with two parents: upstream + current tip
+# Generate correspondence maps for conflict resolution
+UPSTREAM_MAP="$WORKTREE_DIR/upstream-correspondence.map"
+SIBLING_MAP="$WORKTREE_DIR/sibling-correspondence.map"
+
+# Map 1: Our commits vs upstream (for trivial skips)
+generate_correspondence_map "$OLD_MARKER..$TIP_OID" "$OLD_UPSTREAM..$NEW_UPSTREAM" "$UPSTREAM_MAP"
+
+# Map 2: Our commits vs sibling branch (seen→next→main hierarchy)
+case "${SHEARS_BRANCH##*/}" in
+main) SIBLING_BRANCH="origin/shears/next" ;;
+next) SIBLING_BRANCH="origin/shears/seen" ;;
+*)    SIBLING_BRANCH="" ;;
+esac
+if test -n "$SIBLING_BRANCH" && git rev-parse --verify "$SIBLING_BRANCH" >/dev/null 2>&1; then
+	SIBLING_MARKER=$(git rev-parse "$SIBLING_BRANCH^{/Start.the.merging-rebase}" 2>/dev/null) || SIBLING_MARKER=""
+	if test -n "$SIBLING_MARKER"; then
+		generate_correspondence_map "$OLD_MARKER..$TIP_OID" "$SIBLING_MARKER..$SIBLING_BRANCH" "$SIBLING_MAP"
+	fi
+fi
+
+# Create new marker with two parents: upstream + origin/main
 echo "::group::Creating marker and running rebase"
 MARKER_OID=$(git commit-tree "$UPSTREAM_BRANCH^{tree}" \
 	-p "$UPSTREAM_BRANCH" \
-	-p "$TIP_OID" \
+	-p "$GFW_MAIN_BRANCH" \
 	-m "Start the merging-rebase to $UPSTREAM_BRANCH
 
 This commit starts the rebase of $OLD_MARKER to $NEW_UPSTREAM")
 
 git replace --graft "$MARKER_OID" "$UPSTREAM_BRANCH"
 REBASE_TODO_COUNT=$(git rev-list --count "$OLD_MARKER..$TIP_OID")
 echo "Rebasing $REBASE_TODO_COUNT commits onto $MARKER_OID"
-echo "::endgroup::"
 
 run_rebase_with_ai -r --onto "$MARKER_OID" "$OLD_MARKER"
+echo "::endgroup::"
 
 # Clean up graft and verify
 git replace -d "$MARKER_OID"