feat(commit): add amend and undo last commit support

This change introduces new Tauri commands to amend the last commit with
an optional message, fetch the last commit message, and undo the most
recent commit safely. The UI now offers an amend toggle and an undo
button only when the last commit hasn’t been pushed upstream, reducing
the risk of rewriting shared history.

- Add amend/undo/last-message git commands in Rust
- Wire new operations into the Svelte commit panel UI
- Add styling and state handling for amend mode

src-tauri/src/git.rs

@@ -1040,6 +1040,63 @@ pub fn commit(path: String, message: String) -> Result<GitStatus, String> {
     status_for_repo(&repo)
 }
 
+#[tauri::command]
+pub fn amend_commit(path: String, message: Option<String>) -> Result<GitStatus, String> {
+    let repo = resolve_repo(&path)?;
+    if verify_commit(&repo, "HEAD").is_err() {
+        return Err("There is no commit to amend.".to_string());
+    }
+
+    let current_status = status_for_repo(&repo)?;
+    if has_unresolved_conflicts(&current_status) {
+        return Err("Merge conflicts must be resolved before you can commit.".to_string());
+    }
+
+    let message = message
+        .map(|message| message.trim().to_string())
+        .filter(|message| !message.is_empty());
+
+    match message {
+        Some(message) => {
+            run_git(&repo, ["commit", "--amend", "-m", message.as_str()])?;
+        }
+        None => {
+            run_git(&repo, ["commit", "--amend", "--no-edit"])?;
+        }
+    }
+
+    status_for_repo(&repo)
+}
+
+#[tauri::command]
+pub fn last_commit_message(path: String) -> Result<Option<String>, String> {
+    let repo = resolve_repo(&path)?;
+    if verify_commit(&repo, "HEAD").is_err() {
+        return Ok(None);
+    }
+
+    let output = run_git(&repo, ["log", "-1", "--format=%B", "HEAD"])?;
+    let message = String::from_utf8_lossy(&output).trim_end().to_string();
+    Ok(if message.is_empty() { None } else { Some(message) })
+}
+
+#[tauri::command]
+pub fn undo_last_commit(path: String) -> Result<GitStatus, String> {
+    let repo = resolve_repo(&path)?;
+    if verify_commit(&repo, "HEAD").is_err() {
+        return Err("There is no commit to undo.".to_string());
+    }
+    if verify_commit(&repo, "HEAD~1").is_err() {
+        return Err("This is the first commit; there is nothing to undo to.".to_string());
+    }
+
+    // Mixed reset: moves HEAD back one commit and unstages the difference, but
+    // leaves the working tree files untouched, so the undone commit's changes
+    // reappear as ordinary uncommitted changes instead of being discarded.
+    run_git(&repo, ["reset", "HEAD~1"])?;
+    status_for_repo(&repo)
+}
+
 #[tauri::command]
 pub fn pull(
     path: String,

src-tauri/src/main.rs

@@ -5,18 +5,19 @@ mod git;
 
 use badge::set_sync_badge;
 use git::{
-    SearchCancellationState, apply_file_patch, cancel_code_search, cancel_file_history,
-    checkout_branch, cherry_pick_abort, cherry_pick_commit, cherry_pick_continue,
-    clone_repository, commit, commit_ai_generate, commit_ai_load, commit_ai_local_models,
-    commit_ai_status, compare_commits, compare_file_to_head, compare_file_to_parent,
-    create_branch, create_tag, cred_delete, cred_load, cred_save, delete_branch, delete_tag,
-    diff_file_against_working_tree, fetch, get_file_patch, get_remote_url, get_status,
-    list_branches, list_commits, list_file_history, list_repository_files, list_stashes,
-    list_tags, merge_branch, open_repo_in_explorer, open_repository, open_repository_bundle,
-    open_repository_file, pull, push, push_tag, read_conflict, rebase_abort, rebase_branch,
-    rebase_continue, rename_branch, resolve_conflict, resolve_conflict_side,
-    restore_file_from_commit, restore_files, restore_to_commit, search_code_introductions,
-    stage_files, stash_apply, stash_drop, stash_pop, stash_push, unstage_files,
+    SearchCancellationState, amend_commit, apply_file_patch, cancel_code_search,
+    cancel_file_history, checkout_branch, cherry_pick_abort, cherry_pick_commit,
+    cherry_pick_continue, clone_repository, commit, commit_ai_generate, commit_ai_load,
+    commit_ai_local_models, commit_ai_status, compare_commits, compare_file_to_head,
+    compare_file_to_parent, create_branch, create_tag, cred_delete, cred_load, cred_save,
+    delete_branch, delete_tag, diff_file_against_working_tree, fetch, get_file_patch,
+    get_remote_url, get_status, last_commit_message, list_branches, list_commits,
+    list_file_history, list_repository_files, list_stashes, list_tags, merge_branch,
+    open_repo_in_explorer, open_repository, open_repository_bundle, open_repository_file, pull,
+    push, push_tag, read_conflict, rebase_abort, rebase_branch, rebase_continue, rename_branch,
+    resolve_conflict, resolve_conflict_side, restore_file_from_commit, restore_files,
+    restore_to_commit, search_code_introductions, stage_files, stash_apply, stash_drop,
+    stash_pop, stash_push, undo_last_commit, unstage_files,
 };
 
 fn main() {
@@ -54,6 +55,9 @@ fn main() {
             get_file_patch,
             apply_file_patch,
             commit,
+            amend_commit,
+            undo_last_commit,
+            last_commit_message,
             commit_ai_status,
             commit_ai_load,
             commit_ai_local_models,