refactor: rename restack --all-parents flag to --ancestors

The clap long name derived from the `all_parents` field was `--all-parents`,
but the README documented `--ancestors` and that name reads better (a branch
has one parent; the flag really means all ancestors up to trunk). Rename the
field/param to `ancestors` so clap emits `--ancestors`, matching the README.
No backwards-compat concern.

Author: wbbradley

src/llms.md

@@ -96,7 +96,7 @@ itself has no notion of the stack; `git-stack` is the bookkeeping that remembers
   - `-b`/`--branch <name>` — restack this branch instead of the current one.
   - `-f`/`--fetch` — fetch from the remote first.
   - `-p`/`--push` — push the branch(es) to the remote after a successful restack.
-  - `-a`/`--all-parents` — recursively restack every ancestor from trunk up.
+  - `-a`/`--ancestors` — recursively restack every ancestor from trunk up.
   - `-s`/`--squash` — squash all of the branch's commits into one.
   - `--continue` — resume a squash interrupted by a conflict (after resolving).
   - `--abort` — cancel an in-progress squash and restore the original state.

src/main.rs

@@ -75,9 +75,9 @@ enum Command {
         /// Push any changes up to the remote after restacking.
         #[arg(long, short)]
         push: bool,
-        /// Restack all parent branches recursively up to trunk.
+        /// Recursively restack all ancestors from trunk up to this branch.
         #[arg(long, short = 'a', default_value_t = false)]
-        all_parents: bool,
+        ancestors: bool,
         /// Squash all commits in the branch into a single commit.
         #[arg(long, short = 's', default_value_t = false)]
         squash: bool,
@@ -348,7 +348,7 @@ fn inner_main() -> Result<()> {
             branch,
             fetch,
             push,
-            all_parents,
+            ancestors,
             squash,
             r#continue,
             abort,
@@ -372,7 +372,7 @@ fn inner_main() -> Result<()> {
                 current_branch,
                 fetch,
                 push,
-                all_parents,
+                ancestors,
                 squash,
             )
         }
@@ -908,7 +908,7 @@ fn restack(
     orig_branch: String,
     fetch: bool,
     push: bool,
-    all_parents: bool,
+    ancestors: bool,
     squash: bool,
 ) -> Result<(), anyhow::Error> {
     // Hold a repo-scoped advisory lock for the whole restack so a second
@@ -950,7 +950,7 @@ fn restack(
     }
 
     // Find starting_branch in the stacks of branches to determine which stack to use.
-    let plan = state.plan_restack(git_repo, repo, &restack_branch, all_parents)?;
+    let plan = state.plan_restack(git_repo, repo, &restack_branch, ancestors)?;
 
     // Collect plan into owned data to allow mutable access to state during the loop
     let plan_owned: Vec<(String, state::Branch)> = plan

src/state.rs

@@ -324,12 +324,12 @@ impl State {
         git_repo: &GitRepo,
         repo: &str,
         starting_branch: &str,
-        all_parents: bool,
+        ancestors: bool,
     ) -> Result<Vec<RestackStep<'_>>> {
-        tracing::debug!("Planning restack for {starting_branch} (all_parents={all_parents})");
+        tracing::debug!("Planning restack for {starting_branch} (ancestors={ancestors})");
 
         // Single-step mode: only restack the target branch onto its immediate parent
-        if !all_parents {
+        if !ancestors {
             let parent = self
                 .get_parent_branch_of(repo, starting_branch)
                 .ok_or_else(|| {