commit amend: Detect rebase with unresolved conflicts (#710)

If commit amend is called during a rebase operation
with unresolved conflicts, the user probably didn't want to do that.
Offer to abort the operation.

Resolves #700

Author: abhinav

.changes/unreleased/Changed-20250622-152432.yaml

@@ -1,6 +1,7 @@
 kind: Changed
 body: >-
   commit amend:
-  To prevent mistakes, when 'gs commit amend' is called from the trunk branch,
-  confirm user intent, providing an option to create a new branch instead.
+  Confirm user intent when called from the trunk branch,
+  providing an option to create a new branch instead.
+  This prevents accidental changes to the trunk branch.
 time: 2025-06-22T15:24:32.431866-07:00

.changes/unreleased/Changed-20250622-165742.yaml

@@ -0,0 +1,6 @@
+kind: Changed
+body: >-
+  commit amend:
+  Confirm user intent when called during a rebase operation with unresolved conflicts.
+  This prevents accidental amendments that could complicate the rebase process.
+time: 2025-06-22T16:57:42.741195-07:00

commit_amend.go

@@ -119,6 +119,58 @@ func (cmd *commitAmendCmd) Run(
 		}
 	}
 
+	// Check if we're in the middle of a rebase with unmerged paths
+	var rebasing bool
+	if _, err := wt.RebaseState(ctx); err == nil {
+		rebasing = true
+
+		// If we're in the middle of a rebase,
+		// and there are unmerged paths,
+		// what the user likely wants is 'git add' and 'gs rebase continue'.
+		//
+		// (If there are no unmerged paths, amending is fine.)
+		var numUnmerged int
+		for _, err := range wt.ListFilesPaths(ctx, &git.ListFilesOptions{Unmerged: true}) {
+			if err == nil {
+				numUnmerged++
+			}
+		}
+
+		if numUnmerged > 0 {
+			if !ui.Interactive(view) {
+				log.Warnf("You are in the middle of a rebase with unmerged paths.")
+				log.Warnf(`You probably want resolve the conflicts and run "git add", then "gs rebase continue" instead.`)
+			} else {
+				var continueAmend bool
+				fields := []ui.Field{
+					ui.NewList[bool]().
+						WithTitle("Do you want to amend the commit?").
+						WithDescription("You are in the middle of a rebase with unmerged paths.\n"+
+							"You might want to resolve the conflicts and run 'git add', then 'gs rebase continue' instead.").
+						WithItems(
+							ui.ListItem[bool]{
+								Title:       "Yes",
+								Description: func(bool) string { return "Continue with commit amend" },
+								Value:       true,
+							},
+							ui.ListItem[bool]{
+								Title:       "No",
+								Description: func(bool) string { return "Abort the operation" },
+								Value:       false,
+							},
+						).
+						WithValue(&continueAmend),
+				}
+				if err := ui.Run(view, fields...); err != nil {
+					return fmt.Errorf("run prompt: %w", err)
+				}
+				if !continueAmend {
+					return errors.New("operation aborted")
+				}
+			}
+		}
+	}
+
 	if err := wt.Commit(ctx, git.CommitRequest{
 		Message:    cmd.Message,
 		AllowEmpty: cmd.AllowEmpty,
@@ -130,7 +182,7 @@ func (cmd *commitAmendCmd) Run(
 		return fmt.Errorf("commit: %w", err)
 	}
 
-	if _, err := wt.RebaseState(ctx); err == nil {
+	if rebasing {
 		log.Debug("A rebase is in progress, skipping restack")
 		return nil
 	}

testdata/script/commit_amend_rebase_prompt.txt

@@ -0,0 +1,60 @@
+# commit amend during rebase with unmerged paths should suggest 'git add'
+
+as 'Test <[email protected]>'
+at '2025-06-22T21:28:29Z'
+
+cd repo
+git init
+git commit --allow-empty -m 'Initial commit'
+gs repo init
+
+# Create a conflict scenario.
+git add conflict.txt
+gs branch create feature -m 'Add conflict.txt with content A'
+
+gs trunk
+mv conflict-main.txt conflict.txt
+git add conflict.txt
+git commit -m 'Add conflict.txt with content B'
+
+gs bco feature
+! gs branch restack
+
+# Interactive mode should prompt with suggestion to run 'git add'
+env ROBOT_INPUT=$WORK/golden/robot.txt ROBOT_OUTPUT=$WORK/robot.actual
+
+! gs commit amend --no-edit -a -m 'Another amend attempt'
+cmp $WORK/robot.actual $WORK/golden/robot.txt
+
+git status --porcelain
+cmp stdout $WORK/golden/status-conflicted.txt
+
+cp $WORK/other/conflict-resolved.txt conflict.txt
+git add conflict.txt
+gs rebase continue --no-edit
+
+git graph --branches
+cmp stdout $WORK/golden/graph-after-rebase.txt
+
+-- repo/conflict.txt --
+Content A
+-- repo/conflict-main.txt --
+Content B
+-- other/conflict-resolved.txt --
+Content A and B
+-- golden/robot.txt --
+===
+> Do you want to amend the commit?: 
+> ▶ Yes                                                                         
+>   Continue with commit amend                                                   
+>   No                                                                          
+>   Abort the operation                                                         
+> You are in the middle of a rebase with unmerged paths.
+> You might want to resolve the conflicts and run 'git add', then 'gs rebase continue' instead.
+"No"
+-- golden/status-conflicted.txt --
+AA conflict.txt
+-- golden/graph-after-rebase.txt --
+* f8fc3c9 (HEAD -> feature) Add conflict.txt with content A
+* 2f55407 (main) Add conflict.txt with content B
+* f8331be Initial commit