Fix local branch rebasing after land

src/stack_pr/cli.py

@@ -1285,6 +1285,13 @@ def command_land(args: CommonArgs) -> None:
     # already be there from the metadata that commits need to have by that
     # point.
     set_base_branches(st, args.target)
+
+    # If the current branch contains commits from the stack, rebase it onto the
+    # updated stack tip in the end so it reuses the same rewritten commits as
+    # the PR branches.
+    top_commit = st[-1].commit.commit_id()
+    need_to_rebase_current = is_ancestor(top_commit, current_branch, verbose=args.verbose)
+
     print_stack(st, links=args.hyperlinks)
 
     # Verify that the stack is correct before trying to land it.
@@ -1293,13 +1300,25 @@ def command_land(args: CommonArgs) -> None:
     # All good, land the bottommost PR!
     land_pr(st[0], remote=args.remote, target=args.target, verbose=args.verbose)
 
+    # Refresh the local view of the target branch after the merge.
+    run_shell_command(["git", "fetch", "--prune", args.remote], quiet=not args.verbose)
+
+    current_branch_base = f"{args.remote}/{args.target}"
+
     # The rest of the stack now needs to be rebased.
     if len(st) > 1:
         log(h("Rebasing the rest of the stack"), level=1)
         prs_to_rebase = st[1:]
         print_stack(prs_to_rebase, links=args.hyperlinks, level=1)
         for e in prs_to_rebase:
             rebase_pr(e, remote=args.remote, target=args.target, verbose=args.verbose)
+
+        # Resolve the rewritten tip to a commit hash before the local stack
+        # branches are deleted below.
+        current_branch_base = get_command_output(
+            ["git", "rev-parse", prs_to_rebase[-1].head]
+        ).strip()
+
         # Change the target of the new bottom-most PR in the stack to 'target'
         run_shell_command(
             ["gh", "pr", "edit", prs_to_rebase[0].pr, "-B", args.target],
@@ -1317,10 +1336,12 @@ def command_land(args: CommonArgs) -> None:
             ["git", "rebase", f"{args.remote}/{args.target}", args.target],
             quiet=not args.verbose,
         )
-    run_shell_command(
-        ["git", "rebase", f"{args.remote}/{args.target}", current_branch],
-        quiet=not args.verbose,
-    )
+
+    rebase_base = current_branch_base if need_to_rebase_current else f"{args.remote}/{args.target}"
+    cmd = ["git", "rebase", rebase_base, current_branch]
+    if need_to_rebase_current:
+        cmd.append("--committer-date-is-author-date")
+    run_shell_command(cmd, quiet=not args.verbose)
 
     log(h(blue("SUCCESS!")))
 

tests/test_land.py

@@ -0,0 +1,112 @@
+import sys
+from pathlib import Path
+from types import SimpleNamespace
+
+sys.path.append(str(Path(__file__).parent.parent / "src"))
+
+from stack_pr import cli
+
+
+def make_args() -> cli.CommonArgs:
+    return cli.CommonArgs(
+        base="base",
+        head="head",
+        remote="origin",
+        target="main",
+        hyperlinks=False,
+        verbose=False,
+        branch_name_template="$USERNAME/stack/$ID",
+        show_tips=False,
+        land_disabled=False,
+    )
+
+
+def make_entry(head: str, pr: str, commit_id: str) -> SimpleNamespace:
+    return SimpleNamespace(
+        head=head,
+        pr=pr,
+        commit=SimpleNamespace(commit_id=lambda: commit_id),
+    )
+
+
+def test_land_rebases_current_branch_onto_updated_stack_tip(
+    monkeypatch,
+) -> None:
+    commands: list[list[str]] = []
+    stack = [make_entry("stack/1", "pr-1", "commit-1"), make_entry("stack/2", "pr-2", "commit-2")]
+
+    monkeypatch.setattr(cli, "get_current_branch_name", lambda: "feature")
+    monkeypatch.setattr(cli, "should_update_local_base", lambda **kwargs: False)
+    monkeypatch.setattr(cli, "get_stack", lambda **kwargs: stack)
+    monkeypatch.setattr(cli, "set_base_branches", lambda *args, **kwargs: None)
+    monkeypatch.setattr(cli, "print_stack", lambda *args, **kwargs: None)
+    monkeypatch.setattr(cli, "verify", lambda *args, **kwargs: None)
+    monkeypatch.setattr(cli, "land_pr", lambda *args, **kwargs: None)
+    monkeypatch.setattr(cli, "rebase_pr", lambda *args, **kwargs: None)
+    monkeypatch.setattr(cli, "delete_local_branches", lambda *args, **kwargs: None)
+    monkeypatch.setattr(cli, "branch_exists", lambda branch: False)
+    monkeypatch.setattr(
+        cli,
+        "get_command_output",
+        lambda cmd, **kwargs: "rebased-stack-tip\n"
+        if cmd == ["git", "rev-parse", "stack/2"]
+        else "",
+    )
+    monkeypatch.setattr(
+        cli,
+        "is_ancestor",
+        lambda ancestor, descendant, *, verbose: ancestor == "commit-2"
+        and descendant == "feature",
+    )
+
+    def fake_run_shell_command(cmd, *, quiet, check=True, **kwargs):
+        commands.append(list(cmd))
+        return SimpleNamespace(returncode=0, stdout=b"", stderr=b"")
+
+    monkeypatch.setattr(cli, "run_shell_command", fake_run_shell_command)
+
+    cli.command_land(make_args())
+
+    assert [
+        "git",
+        "rebase",
+        "rebased-stack-tip",
+        "feature",
+        "--committer-date-is-author-date",
+    ] in commands
+    assert ["git", "rebase", "stack/2", "feature", "--committer-date-is-author-date"] not in commands
+    assert ["git", "rebase", "origin/main", "feature"] not in commands
+
+
+def test_land_refreshes_remote_target_before_rebasing_current_branch(
+    monkeypatch,
+) -> None:
+    commands: list[list[str]] = []
+    stack = [make_entry("stack/1", "pr-1", "commit-1")]
+
+    monkeypatch.setattr(cli, "get_current_branch_name", lambda: "feature")
+    monkeypatch.setattr(cli, "should_update_local_base", lambda **kwargs: False)
+    monkeypatch.setattr(cli, "get_stack", lambda **kwargs: stack)
+    monkeypatch.setattr(cli, "set_base_branches", lambda *args, **kwargs: None)
+    monkeypatch.setattr(cli, "print_stack", lambda *args, **kwargs: None)
+    monkeypatch.setattr(cli, "verify", lambda *args, **kwargs: None)
+    monkeypatch.setattr(cli, "land_pr", lambda *args, **kwargs: None)
+    monkeypatch.setattr(cli, "delete_local_branches", lambda *args, **kwargs: None)
+    monkeypatch.setattr(cli, "branch_exists", lambda branch: False)
+    monkeypatch.setattr(
+        cli,
+        "is_ancestor",
+        lambda ancestor, descendant, *, verbose: ancestor == "commit-1"
+        and descendant == "feature",
+    )
+
+    def fake_run_shell_command(cmd, *, quiet, check=True, **kwargs):
+        commands.append(list(cmd))
+        return SimpleNamespace(returncode=0, stdout=b"", stderr=b"")
+
+    monkeypatch.setattr(cli, "run_shell_command", fake_run_shell_command)
+
+    cli.command_land(make_args())
+
+    assert ["git", "fetch", "--prune", "origin"] in commands
+    assert ["git", "rebase", "origin/main", "feature", "--committer-date-is-author-date"] in commands