Prevent automatic maintenance from racing rebases

Author: skarim

AGENTS.md

@@ -144,5 +144,6 @@ if errors.As(err, &exitErr) { ... }
 - `git.SetOps()` replaces the **package-level** ops variable. Forgetting `defer restore()` in a test will break every subsequent test in the package.
 - Interrupt detection: Ctrl+C is caught as `terminal.InterruptErr`, wrapped into an `errInterrupt` sentinel, and printed with a friendly message before a silent exit.
 - Rerere: on first rebase conflict, the user is prompted to enable `git rerere`. If declined, a flag file prevents future prompts. `tryAutoResolveRebase()` loops up to 1000 times auto-continuing when rerere resolves conflicts.
+- Rebase commands disable automatic maintenance through command-local configuration so detached `rerere gc` cannot race conflict handling. Repository settings and unrelated Git commands are unchanged.
 - Date-preserving rebase starts use the merge backend so Git persists the date setting across conflicts. Continuations use native saved settings, not start-only date flags.
 - The `.gitignore` ignores `/gh-stack` and `/gh-stack.exe` (the built binary).

internal/git/git.go

@@ -151,8 +151,9 @@ func (d *defaultOps) runRebaseCommand(args []string, opts RebaseOpts) error {
 
 func rebaseArgs(opts RebaseOpts) []string {
 	// The cascade owns its ref range and must never stash another worktree.
+	// Detached maintenance can race the next commit's rerere lock.
 	// Use configuration overrides rather than flags unavailable in Git 2.36.
-	args := []string{"-c", "rebase.updateRefs=false", "-c", "rebase.autoStash=false", "rebase"}
+	args := []string{"-c", "rebase.updateRefs=false", "-c", "rebase.autoStash=false", "-c", "maintenance.auto=false", "rebase"}
 	if opts.CommitterDateIsAuthorDate {
 		// The apply backend loses this option after a conflict. The merge
 		// backend persists it for continuation and rerere auto-continuation.

internal/git/gitops_test.go

@@ -1,11 +1,13 @@
 package git
 
 import (
+	"encoding/json"
 	"fmt"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"runtime"
+	"slices"
 	"strings"
 	"testing"
 
@@ -1429,6 +1431,9 @@ func TestIntegration_WorktreeRerereAutoContinuesMultipleCommits(t *testing.T) {
 	original := gitExec(t, path, "rev-parse", "HEAD")
 	mainHead := gitExec(t, dir, "rev-parse", "HEAD")
 	require.NoError(t, linked.EnableRerere())
+	gitExec(t, dir, "config", "maintenance.auto", "true")
+	tracePath := filepath.Join(t.TempDir(), "rebase-trace")
+	t.Setenv("GIT_TRACE2_EVENT", tracePath)
 	t.Setenv("GIT_EDITOR", "false")
 	restore := forbidGlobalWorktreeQueries(t)
 	defer restore()
@@ -1465,6 +1470,31 @@ func TestIntegration_WorktreeRerereAutoContinuesMultipleCommits(t *testing.T) {
 		require.NoError(t, err)
 		assert.Contains(t, string(data), "resolved")
 	}
+	trace, err := os.ReadFile(tracePath)
+	require.NoError(t, err)
+	var rebaseSessions []string
+	for _, line := range strings.Split(strings.TrimSpace(string(trace)), "\n") {
+		var event struct {
+			Event string   `json:"event"`
+			SID   string   `json:"sid"`
+			Argv  []string `json:"argv"`
+		}
+		require.NoError(t, json.Unmarshal([]byte(line), &event))
+		if event.Event == "start" && slices.Contains(event.Argv, "rebase") {
+			rebaseSessions = append(rebaseSessions, event.SID)
+		}
+		if event.Event != "child_start" || len(event.Argv) < 3 ||
+			event.Argv[1] != "maintenance" || event.Argv[2] != "run" || !slices.Contains(event.Argv, "--auto") {
+			continue
+		}
+		for _, sid := range rebaseSessions {
+			assert.False(t, event.SID == sid || strings.HasPrefix(event.SID, sid+"/"),
+				"automatic maintenance can race the next commit's rerere lock: %v", event.Argv)
+		}
+	}
+	assert.NotEmpty(t, rebaseSessions)
+	assert.Equal(t, "true", gitExec(t, dir, "config", "--local", "--get", "maintenance.auto"),
+		"the rebase must not change the repository's maintenance configuration")
 }
 
 func TestIntegration_WorktreeRebaseContinueStopsWhenNoProgress(t *testing.T) {

internal/git/worktree_test.go

@@ -209,7 +209,7 @@ func TestStateQueryWrappersDelegateErrors(t *testing.T) {
 func TestRebaseArgs(t *testing.T) {
 	for _, date := range []bool{false, true} {
 		args := rebaseArgs(RebaseOpts{CommitterDateIsAuthorDate: date})
-		want := []string{"-c", "rebase.updateRefs=false", "-c", "rebase.autoStash=false", "rebase"}
+		want := []string{"-c", "rebase.updateRefs=false", "-c", "rebase.autoStash=false", "-c", "maintenance.auto=false", "rebase"}
 		if date {
 			want = append(want, "--merge", "--committer-date-is-author-date")
 		}