Add switch branch (b): stage the tip and restore to it

b opens a centered popup with a search line and the local and remote
branches of the selection. Enter stages the branch tip as the pin of a
submodule, restores it (and everything below) to it, and puts HEAD on the
branch; a remote branch gets a local tracking branch unless one exists
elsewhere. Works on the superproject too. Losses are asked like restore.
The backdrop behind the popup is dimmed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
2026-10-22 14:18:49 +02:00
co-authored by Claude Opus 5.5
parent b9f6055759
commit 2b6b781826
21 changed files with 1311 additions and 43 deletions
+132
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@@ -0,0 +1,132 @@
package git
import (
"context"
"errors"
"fmt"
"slices"
"strconv"
"strings"
"time"
"submarine/internal/submodule"
)
// switchDir returns the directory of path ("" is the superproject), and the
// submodule's info if it is one.
func (p *Provider) switchDir(path string) (dir string, in info, sub bool, err error) {
if path == "" {
return p.root, info{}, false, nil
}
p.mu.RLock()
in, ok := p.mods[path]
p.mu.RUnlock()
if !ok {
return "", info{}, false, fmt.Errorf("unknown submodule %q", path)
}
if !initialized(in.dir) {
return "", info{}, false, errors.New("not initialized; restore it first")
}
return in.dir, in, true, nil
}
// Branches lists the local and remote-tracking branches of path, local ones
// first, each group by the date of its tip, newest first. It reads only what
// is on disk.
func (p *Provider) Branches(ctx context.Context, path string) ([]submodule.Branch, error) {
dir, _, _, err := p.switchDir(path)
if err != nil {
return nil, err
}
out, err := run(ctx, dir, "for-each-ref",
"--format=%(refname)%00%(objectname)%00%(committerdate:unix)%00%(HEAD)%00%(symref)",
"refs/heads", "refs/remotes")
if err != nil {
return nil, err
}
var branches []submodule.Branch
for _, line := range strings.Split(out, "\n") {
f := strings.Split(line, "\x00")
if len(f) != 5 || f[4] != "" { // a symref is origin/HEAD
continue
}
b := submodule.Branch{Ref: f[0], SHA: f[1], Current: f[3] == "*"}
if secs, err := strconv.ParseInt(f[2], 10, 64); err == nil {
b.When = time.Unix(secs, 0)
}
if name, ok := strings.CutPrefix(f[0], "refs/heads/"); ok {
b.Name, b.Local = name, name
} else if name, ok := strings.CutPrefix(f[0], "refs/remotes/"); ok {
_, local, _ := strings.Cut(name, "/")
b.Name, b.Local, b.Remote = name, local, true
} else {
continue
}
branches = append(branches, b)
}
slices.SortStableFunc(branches, func(a, b submodule.Branch) int {
switch {
case a.Remote != b.Remote:
if a.Remote {
return 1
}
return -1
default:
return b.When.Compare(a.When)
}
})
return branches, nil
}
// SwitchLoss reports what switching path to b would discard: the same as a
// restore to b's tip.
func (p *Provider) SwitchLoss(ctx context.Context, path string, b submodule.Branch) (submodule.Loss, error) {
dir, _, _, err := p.switchDir(path)
if err != nil {
return submodule.Loss{}, err
}
return p.lossOf(ctx, dir, b.SHA), nil
}
// Switch makes b's tip the staged pin of a submodule, restores the repository
// to it (see Restore) and puts HEAD on the branch. For a remote branch the
// local branch of that name is created, tracking it. A local branch that
// exists elsewhere is never moved: HEAD stays detached and "" is returned.
func (p *Provider) Switch(ctx context.Context, path string, b submodule.Branch) (string, error) {
dir, in, sub, err := p.switchDir(path)
if err != nil {
return "", err
}
if sha, ok, err := try(ctx, dir, "rev-parse", "--verify", "-q", b.Ref+"^{commit}"); err != nil {
return "", err
} else if !ok || sha != b.SHA {
return "", fmt.Errorf("%s moved; open the list again", b.Name)
}
if sub { // staged first, so a failed restore can be repeated with x
if _, err := p.exec(ctx, in.superDir, nil, "update-index", "--cacheinfo", "160000,"+b.SHA+","+in.relPath); err != nil {
return "", err
}
}
if err := p.restoreRepo(ctx, dir, b.SHA); err != nil {
return "", err
}
g := func(args ...string) (string, error) {
return p.exec(ctx, dir, nil, append(append([]string{}, restoreArgs...), args...)...)
}
if !b.Remote {
_, err := g("switch", "-q", b.Local)
return b.Local, err
}
switch tip, ok, err := try(ctx, dir, "rev-parse", "--verify", "-q", "refs/heads/"+b.Local); {
case err != nil:
return "", err
case !ok:
_, err := g("switch", "-q", "-c", b.Local, "--track", b.Name)
return b.Local, err
case tip == b.SHA:
_, err := g("switch", "-q", b.Local)
return b.Local, err
}
return "", nil
}
+181
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@@ -0,0 +1,181 @@
package git
import (
"context"
"os"
"path/filepath"
"strings"
"testing"
"submarine/internal/submodule"
)
func findBranch(t *testing.T, bs []submodule.Branch, name string) submodule.Branch {
t.Helper()
for _, b := range bs {
if b.Name == name {
return b
}
}
t.Fatalf("no branch %q in %v", name, bs)
return submodule.Branch{}
}
func TestBranchesListsLocalAndRemote(t *testing.T) {
p, root := ownFixture(t)
_ = root
bs, err := p.Branches(context.Background(), "libs/feature")
if err != nil {
t.Fatal(err)
}
var names []string
seenRemote := false
for _, b := range bs {
names = append(names, b.Name)
if b.Remote {
seenRemote = true
} else if seenRemote {
t.Errorf("local branch %s after a remote one: %v", b.Name, names)
}
if b.Name == "origin/HEAD" {
t.Error("origin/HEAD must not be listed")
}
}
rb := findBranch(t, bs, "origin/feat/search")
if !rb.Remote || rb.Local != "feat/search" {
t.Errorf("origin/feat/search = %+v", rb)
}
findBranch(t, bs, "origin/main")
}
func TestSwitchSubmoduleStagesTipAndTracksRemoteBranch(t *testing.T) {
p, root := ownFixture(t)
super := filepath.Join(root, "super")
sub := filepath.Join(super, "libs", "feature")
ctx := context.Background()
bs, err := p.Branches(ctx, "libs/feature")
if err != nil {
t.Fatal(err)
}
b := findBranch(t, bs, "origin/feat/search")
got, err := p.Switch(ctx, "libs/feature", b)
if err != nil {
t.Fatal(err)
}
if got != "feat/search" {
t.Errorf("Switch returned %q, want feat/search", got)
}
if head := out(t, sub, "branch", "--show-current"); head != "feat/search" {
t.Errorf("branch = %q", head)
}
if up := out(t, sub, "rev-parse", "--abbrev-ref", "feat/search@{upstream}"); up != "origin/feat/search" {
t.Errorf("upstream = %q", up)
}
if head := out(t, sub, "rev-parse", "HEAD"); head != b.SHA {
t.Errorf("HEAD = %s, want %s", head, b.SHA)
}
if staged := out(t, super, "ls-files", "-s", "--", "libs/feature"); !strings.Contains(staged, b.SHA) {
t.Errorf("index = %q, want the tip %s staged", staged, b.SHA)
}
assertExact(t, sub)
}
func TestSwitchNeverMovesAnExistingLocalBranch(t *testing.T) {
p, root := ownFixture(t)
sub := filepath.Join(root, "super", "libs", "feature")
ctx := context.Background()
git(t, sub, "branch", "feat/search", "origin/main") // same name, elsewhere
before := out(t, sub, "rev-parse", "feat/search")
bs, err := p.Branches(ctx, "libs/feature")
if err != nil {
t.Fatal(err)
}
b := findBranch(t, bs, "origin/feat/search")
got, err := p.Switch(ctx, "libs/feature", b)
if err != nil {
t.Fatal(err)
}
if got != "" {
t.Errorf("Switch returned %q, want detached", got)
}
if head := out(t, sub, "branch", "--show-current"); head != "" {
t.Errorf("HEAD on %q, want detached", head)
}
if after := out(t, sub, "rev-parse", "feat/search"); after != before {
t.Errorf("branch moved: %s -> %s", before, after)
}
if head := out(t, sub, "rev-parse", "HEAD"); head != b.SHA {
t.Errorf("HEAD = %s, want %s", head, b.SHA)
}
}
func TestSwitchAbortsWhenTheBranchMoved(t *testing.T) {
p, root := ownFixture(t)
sub := filepath.Join(root, "super", "libs", "feature")
ctx := context.Background()
bs, err := p.Branches(ctx, "libs/feature")
if err != nil {
t.Fatal(err)
}
b := findBranch(t, bs, "origin/main")
b.SHA = out(t, sub, "rev-parse", "origin/feat/search") // what the list showed is stale
if _, err := p.Switch(ctx, "libs/feature", b); err == nil || !strings.Contains(err.Error(), "moved") {
t.Errorf("err = %v, want a moved error", err)
}
}
func TestSwitchSuperprojectRestoresSubmodulesToItsPins(t *testing.T) {
p, root := ownFixture(t)
super := filepath.Join(root, "super")
ctx := context.Background()
git(t, super, "branch", "older", "HEAD~1")
bs, err := p.Branches(ctx, "")
if err != nil {
t.Fatal(err)
}
b := findBranch(t, bs, "older")
got, err := p.Switch(ctx, "", b)
if err != nil {
t.Fatal(err)
}
if got != "older" || out(t, super, "branch", "--show-current") != "older" {
t.Errorf("Switch = %q, branch = %q", got, out(t, super, "branch", "--show-current"))
}
assertExact(t, super)
}
func TestSwitchLossCountsChangedFiles(t *testing.T) {
p, root := ownFixture(t)
sub := filepath.Join(root, "super", "libs", "feature")
ctx := context.Background()
bs, err := p.Branches(ctx, "libs/feature")
if err != nil {
t.Fatal(err)
}
b := findBranch(t, bs, "origin/feat/search")
loss, err := p.SwitchLoss(ctx, "libs/feature", b)
if err != nil {
t.Fatal(err)
}
if !loss.Empty() {
t.Errorf("clean checkout: loss = %+v", loss)
}
if err := os.WriteFile(filepath.Join(sub, "new.txt"), []byte("x"), 0o644); err != nil {
t.Fatal(err)
}
if loss, err = p.SwitchLoss(ctx, "libs/feature", b); err != nil || loss.Files != 1 {
t.Errorf("loss = %+v, %v; want 1 file", loss, err)
}
}
func TestBranchesOfAMissingSubmoduleSaysSo(t *testing.T) {
p, _ := ownFixture(t)
if _, err := p.Branches(context.Background(), "libs/missing"); err == nil || !strings.Contains(err.Error(), "not initialized") {
t.Errorf("err = %v", err)
}
}
+29 -1
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@@ -1,6 +1,9 @@
package submodule
import "context"
import (
"context"
"time"
)
// Provider supplies repository data. Tree is expected to be fast (structure
// only); Status may be slow and is called once per submodule, concurrently.
@@ -44,6 +47,31 @@ type Restorer interface {
Restore(ctx context.Context, path string, to RestoreTarget) error
}
// Branch is a local or remote-tracking branch of a repository.
type Branch struct {
Ref string // full ref, e.g. "refs/remotes/origin/feat"
Name string // short name, e.g. "origin/feat"
Local string // name of the local branch it stands for, e.g. "feat"
Remote bool // a remote-tracking branch
Current bool // HEAD is on this branch
SHA string // the tip when the list was read
When time.Time // committer date of the tip
}
// Switcher is implemented by providers that can switch a repository to a
// branch: the tip becomes the staged pin of a submodule, and the repository
// (with everything below it) is restored to it. Path "" is the superproject.
// Like Restore, Switch may clone or fetch what is missing below, but must
// never prompt the user. Branches uses no network.
type Switcher interface {
Branches(ctx context.Context, path string) ([]Branch, error)
// SwitchLoss reports what Switch would discard, read from the disk now.
SwitchLoss(ctx context.Context, path string, b Branch) (Loss, error)
// Switch returns the branch HEAD ends up on, "" if it is detached. It
// fails if b.Ref no longer points at b.SHA.
Switch(ctx context.Context, path string, b Branch) (string, error)
}
// RestoreTarget is the pin a submodule is restored to. It doesn't matter for
// the superproject, whose target is always HEAD.
type RestoreTarget int