Fix flaky TestWatch when a fetch is reported in two rounds

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

README.md

@@ -0,0 +1,135 @@
+# submarine
+
+**A terminal UI for git repositories with many submodules.**
+See what needs your attention. Ignore the rest.
+
+`git submodule status` gives you a wall of commit hashes. submarine answers
+the questions you actually have:
+
+- Which branch is this submodule on, and is the pin current?
+- Which submodules need me, and which are fine?
+- Is anything dangerous, like a pin nobody else can fetch?
+
+![submarine showing a tree with nested submodules and the detail pane of an off-pin submodule that is one commit behind its branch](docs/images/overview.png)
+
+## Why you might like it
+
+- **Only submodules, as a tree.** Nested submodules at any depth, grouped by
+  directory, collapsed until you open them.
+- **Branch plus distance, not hashes.** `origin/main ↓2` says more than
+  `b7c8d9e`. A pin on a feature branch shows that branch.
+- **Problems are loud, healthy is quiet.** Submodules without issues are
+  muted `in sync`; a staged pin shows as blue `staged` (or a `●` after an
+  issue word). A collapsed parent counts the problems hidden below it
+  (`·1`) and shows `●` if a staged pin is hidden.
+- **Words, not symbols.** Every state is a short word (`unpushed`, `conflict`,
+  `missing`, `off pin`, `changed`), so nothing depends on color alone.
+- **Live.** Fetches in the background on startup and follows changes you make
+  in other shells within about two seconds.
+- **Built for dozens to hundreds of submodules.** Each status loads
+  asynchronously, so the UI never freezes.
+
+## Install
+
+```sh
+curl -fsSL https://git.simon-franken.de/simonfranken/submarine/raw/branch/main/install.sh | sh
+```
+
+Installs `sub` and `submarine` (linux/macOS, amd64/arm64) to `~/.local/bin`.
+Both names start the same program; the examples below use the shorter `sub`.
+Update later with `sub update`.
+
+## Try it
+
+```sh
+sub                  # the repository in the current directory
+sub ~/code/project   # any directory inside a repository
+sub --no-fetch       # skip the background fetch
+sub --mock           # built-in sample data, no repository needed
+```
+
+`submarine` works everywhere `sub` does, e.g. `submarine --mock`.
+
+## Examples
+
+### Find what needs attention
+
+Problems stand out: `unpushed` in red, `off pin` and `changed` in yellow,
+everything else muted. Select a submodule to see the details on the right:
+every issue in words, the resolved ref and why, the pinned, checked-out and
+tip commits, and a preview of uncommitted changes.
+
+```
+ src/                                    │ src/
+     core        off pin   origin/main   │ net
+   ▸ net [2]     unpushed  origin/main ↑1│
+     ui          in sync   origin/main   │ unpushed  pin not pushed to any remote
+                                         │
+                                         │ Ref       origin/main ↑1
+                                         │           via checked out branch
+                                         │ Pinned    b7c8d9e Hotfix null pointer
+                                         │ Checkout  b7c8d9e Hotfix null pointer
+                                         │ Tip       6f5e4d3 Release 2.1.0
+```
+
+### Jump to a submodule with `/`
+
+Press `/` and type. Only matching submodules (and the parents that lead to
+them) stay. Your selection moves to the next match if it was filtered out.
+
+```
+ libs/
+   ▾ log          in sync   origin/main
+     modules/
+         nested   changed   origin/main
+ / nest                                          enter navigate • esc close
+```
+
+`enter` keeps the filter and gives you the normal keys back, `esc` removes
+it and leaves your selection where it is.
+
+### Copy a path
+
+Select a submodule and press `c`. Its absolute directory lands in your
+clipboard, ready for `cd <paste>`. It works over SSH too (OSC 52; in tmux,
+`set -g set-clipboard on`).
+
+### Fetch and reload
+
+`f` fetches all repositories again, `r` reloads everything after you edited
+files.
+
+## Keys
+
+| Key | Action |
+|---|---|
+| `↑` `↓` / `j` `k` | Move |
+| `←` `→` / `h` `l` | Fold / unfold, parent / first child |
+| `H` `L` / `⇧←` `⇧→` | Collapse / expand all |
+| `space` | Toggle the selected submodule |
+| `home` `end` / `g` `G`, `pgup` `pgdn` | Jump, page |
+| `/` | Filter |
+| `c` | Copy path |
+| `f` / `r` | Fetch / reload |
+| `?` | Full help |
+| `q` | Quit |
+
+The mouse works too: click to select, click `▸` to toggle, wheel to move.
+
+## Status
+
+A prototype. Browsing is complete; the actions `u` (check out the pin),
+`b` (bump the pin to the tip) and `!` (problems only) are planned.
+
+## Documentation
+
+Requirements, state rules, UX guide, architecture and the decision log are in
+[docs/](docs/README.md).
+
+## Development
+
+```sh
+go run ./cmd/submarine --mock   # run on mock data
+scripts/make-fixture.sh DIR     # build a test superproject with every state
+go vet ./... && go test ./...
+```

docs/README.md

@@ -32,9 +32,9 @@ through a git provider (`internal/submodule/git`): `submarine [dir]`. It
 fetches in the background on startup (`--no-fetch` to skip; `f` to fetch
 again) and follows changes made in other shells. `submarine --mock` shows
 the built-in mock data (`internal/submodule/mock`). The actions `u`, `b`,
-`/`, `!` only show a "not implemented" message.
+`!` only show a "not implemented" message.
 
 Next steps, roughly in order:
 
 1. Actions: checkout pin (`submodule update`), bump pin to tip, init.
-2. Filter (`/`) and "problems only" (`!`) views.
+2. "Problems only" (`!`) view; it can reuse the tree's filter.

docs/decisions.md

@@ -231,3 +231,30 @@ those preferred refs, by commits on either side: scanning every branch's
 merge base would be too slow. Cost: a pin on main far behind its tip shows a
 younger branch that contains it if that branch's tip is closer, so "n behind
 main" is no longer visible there; `via <rule>` still tells which ref it is.
+
+## Filter: matches with ancestors, lives as long as the input
+
+`/` filters by case-insensitive substring of the submodule path. Matches
+keep their ancestors, shown expanded, because a nested submodule alone
+would lose its context; the user's fold state is not touched, so closing the
+filter restores it (plus the selection's ancestors, so the selection stays
+visible). The filter exists exactly while the input line is open, and `esc`
+closes both, so there is no hidden filter that makes the list look
+incomplete. While typing, `j`/`k`/`q` are text; `enter` returns the keys to
+the tree and keeps the filter, so a filtered list can be navigated with the
+usual keys. A filtered-out selection moves to the next visible submodule
+(previous if none follows) instead of the first, so the cursor stays near
+where it was. This adds the `bubbles/textinput` dependency (and its
+`atotto/clipboard` import).
+
+## Staged pin is shown in the tree, but is not an issue
+
+A staged pin was only visible in the detail pane, so the header's `1 pin
+staged` could not be traced to a row, and `in sync  nothing to do` was
+wrong for a submodule whose pin change still has to be committed. The tree
+now shows it in the status column: blue `staged` replaces `in sync`; next to
+an issue word it is a blue `●` (an issue wins the word, since the cell holds
+one word, D3). It is not counted in `+n`, because `+n` and the header count
+issues and a staged pin stays quiet (D4). A collapsed row shows `●` if a
+staged pin is hidden below it (`Hidden.Staged`), placed before the `·k`
+counts so truncation of the 16-column cell cuts the counts first.

docs/requirements.md

@@ -35,7 +35,7 @@ commit hashes. It doesn't answer the questions users actually have:
   e.g. `[2]`.
 - **F6** A collapsed submodule shows the number of issues **hidden** in all
   its descendants (`·1 ·2`), one count per level: errors in red, then
-  warnings in yellow.
+  warnings in yellow. A staged pin below shows as a blue `●` before them.
 - **F7** Expansion state of descendants is remembered when a parent is
   collapsed and restored when it is expanded again (except after
   "collapse all", which resets it).
@@ -44,7 +44,8 @@ commit hashes. It doesn't answer the questions users actually have:
 
 - **F10** Each submodule shows at most **one** state word: the most severe
   issue, plus `+n` if there are more. Submodules without issues show a
-  muted `in sync`.
+  muted `in sync`, or a blue `staged` if their pin change is staged. With
+  issues, a staged pin adds a blue `●` after the word.
   See [state-model.md](state-model.md) for the full rules.
 - **F11** Each submodule shows its pin as a ref (`origin/main`, a tag, or a
   short SHA as a fallback) and the distance to that ref (`↑n`, `↓n`, `↑n↓m`).
@@ -103,13 +104,18 @@ commit hashes. It doesn't answer the questions users actually have:
 - **F53** `f` fetches again; `r` reloads everything (e.g. after editing
   files, which is not watched).
 
+- **F54** `/` filters the tree by name/path (case-insensitive substring).
+  A text input above the footer takes the term; `esc` closes it and removes
+  the filter. A selection that is filtered out moves to the next visible
+  submodule (none if nothing matches); closing the filter keeps the
+  selection. See [Filter](ux-guide.md#filter).
+
 ### Actions (planned, not implemented)
 
 | Key | Action |
 |---|---|
 | `u` | Check out the pinned commit (`git submodule update`) |
 | `b` | Bump the pin to the tip of its ref |
-| `/` | Filter by name/path |
 | `!` | Show only submodules with issues |
 
 ## Usage

docs/state-model.md

@@ -82,6 +82,8 @@ Rules:
   changed.
 - **Not issues** (quiet): in sync, pin behind/ahead/diverged but pushed,
   staged pin, detached HEAD on the pin. They are shown as information only.
+  A staged pin is also visible in the tree (`staged` or a `●` marker), see
+  [ux-guide.md](ux-guide.md#tree-row), but is never counted as an issue.
 - A loading error is shown as `error` (Danger) in the UI; it is not an issue
   kind.
 

docs/ux-guide.md

@@ -34,6 +34,7 @@
 | Header | 1 line |
 | Tree | Remaining width |
 | Detail pane | 40% of the width, at least 36 columns; hidden below 90 columns |
+| Filter line | 1 line above the footer, only while filtering |
 | Footer | 1 line (more with full help) |
 
 ### Key bar and palette
@@ -62,7 +63,7 @@ indent ▸ name [n]   status          ref             delta
 | indent | 2 per depth | |
 | toggle | 3 | `▸` collapsed, `▾` expanded, blank for leaves |
 | name | fits the widest visible name | name, `[n]` = direct children (collapsed only) |
-| status | 16 | issue word, `+n`, `·k` hidden issues per level (red, then yellow); muted `in sync` without issues; spinner while loading |
+| status | 16 | issue word, `+n`, `●` staged pin, `·k` hidden issues per level (red, then yellow); blue `staged` or muted `in sync` without issues; spinner while loading |
 | ref | widest ref, max 22 | resolved ref; muted short SHA if unresolved |
 | delta | 6 | `↑n`, `↓n`, `↑n↓m` |
 
@@ -76,8 +77,8 @@ indent ▸ name [n]   status          ref             delta
 
 1. Directory (muted) and name (bold)
 2. One line per issue: word (colored, 10 columns) + explanation;
-   `in sync  nothing to do` if there are none; `staged` and
-   `detached HEAD on pin` as information
+   `in sync  nothing to do` if there are none and no pin is staged;
+   `staged` and `detached HEAD on pin` as information
 3. `Changes` (only with uncommitted changes), see
    [Change preview](#change-preview)
 4. `Ref` with distance and `via <rule>`; `Fetched <age>` of the submodule;
@@ -164,7 +165,7 @@ colors in components.
 |---|---|---|
 | Danger | ANSI `1` red, bold | `unpushed`, `conflict`, `error`, `↑n` of an unpushed pin |
 | Warn | ANSI `3` yellow | `missing`, `off pin`, `changed`, differing checkout SHA |
-| Info | ANSI `4` blue | `staged` |
+| Info | ANSI `4` blue | `staged`, the `●` staged marker |
 | Primary | ANSI `6` cyan | branch names, commit hashes, spinner |
 | Muted | ANSI `8` grey | quiet rows, directory headers, arrows, labels |
 | Text | terminal default | normal text |
@@ -207,7 +208,8 @@ colors in components.
 | `f` | Fetch all repositories (does nothing while a fetch runs) |
 | `r` | Reload everything (e.g. after editing files) |
 | `c` | Copy the absolute directory of the selected submodule to the clipboard (OSC 52, so it also works over SSH; needs terminal support, in tmux `set -g set-clipboard on`). The footer confirms with `copied <path>`. Without a local provider (mock) the path relative to the superproject is copied |
-| `u`, `b`, `/`, `!` | Planned actions (see requirements) |
+| `/` | Open the filter, see [Filter](#filter) |
+| `u`, `b`, `!` | Planned actions (see requirements) |
 
 "First child" always means the first child **as displayed** (children are
 grouped by directory).
@@ -216,6 +218,26 @@ Collapsing an ancestor of the selection moves the selection to that ancestor.
 The view scrolls so the selection is always visible; when the first submodule
 is selected, headers above it are shown too.
 
+### Filter
+
+`/` shows a text input above the footer (`/ term`). While it is open the
+tree shows only the submodules whose path (which includes the name)
+contains the term, ignoring case; their ancestors stay as context and are
+shown expanded, whatever the user folded. Directory headers without a
+match vanish. If nothing matches the tree says `no submodule matches`.
+
+- **Selection.** If the selected submodule is filtered out, the next
+  visible one (in display order) is selected, else the previous one; if none
+  is left, nothing is selected (the detail pane is empty).
+- **Typing.** The input has the focus: letters edit the term, so `j`, `q`
+  etc. are text. `↑` `↓` `pgup` `pgdn` still move the selection. `enter`
+  hands the keys back to the tree (the filter stays, all keys work again);
+  `/` edits the term again.
+- **`esc`** closes the input and removes the filter, in both modes. The
+  selection stays; its ancestors are expanded so it is still visible.
+- The filter line shows the keys that apply on its right.
+- The header counts are not filtered.
+
 ### Key reference
 
 Every key in the UI, where it is shown, and whether it works. Update this
@@ -237,7 +259,7 @@ where the palette can't be shown, see [Key bar and palette](#key-bar-and-palette
 | `b` | Bump pin to tip | Submodule | Help | no (flashes "not implemented") |
 | `f` | Fetch all repositories | Global | Help | yes |
 | `r` | Reload everything | Global | Help | yes |
-| `/` | Filter | Global | Help | no (flashes "not implemented") |
+| `/` | Filter | Global | Help | yes |
 | `!` | Problems only | Global | Help | no (flashes "not implemented") |
 | `?` | Toggle full help | Global | Bar, Help | yes |
 | `q`, `ctrl+c` | Quit | Global | Bar, Help | yes |

go.mod

@@ -12,6 +12,7 @@ require (
 )
 
 require (
+	github.com/atotto/clipboard v0.1.4 // indirect
 	github.com/charmbracelet/colorprofile v0.4.1 // indirect
 	github.com/charmbracelet/x/cellbuf v0.0.15 // indirect
 	github.com/charmbracelet/x/term v0.2.2 // indirect

go.sum

@@ -1,3 +1,5 @@
+github.com/atotto/clipboard v0.1.4 h1:EH0zSVneZPSuFR11BlR9YppQTVDbh5+16AmcJi4g1z4=
+github.com/atotto/clipboard v0.1.4/go.mod h1:ZY9tmq7sm5xIbd9bOK4onWV4S6X0u6GY7Vn0Yu86PYI=
 github.com/aymanbagabas/go-osc52/v2 v2.0.1 h1:HwpRHbFMcZLEVr42D4p7XBqjyuxQH5SMiErDT4WkJ2k=
 github.com/aymanbagabas/go-osc52/v2 v2.0.1/go.mod h1:uYgXzlJ7ZpABp8OJ+exZzJJhRNQ2ASbcXHWsFqH8hp8=
 github.com/aymanbagabas/go-udiff v0.3.1 h1:LV+qyBQ2pqe0u42ZsUEtPiCaUoqgA9gYRDs3vj1nolY=

internal/submodule/git/fetch_test.go

@@ -139,7 +139,13 @@ func TestWatch(t *testing.T) {
 
 	// a commit in another shell
 	git(t, filepath.Join(super, "libs", "store"), "commit", "-q", "--allow-empty", "-m", "Local")
-	if c := next(t, ch); c != (submodule.Change{Path: "libs/store", Local: true}) {
+	c := next(t, ch)
+	if c == (submodule.Change{Path: "src/net"}) {
+		// git fetch writes FETCH_HEAD and the refs at different moments, so
+		// with a 20ms poll it can be reported in two rounds
+		c = next(t, ch)
+	}
+	if c != (submodule.Change{Path: "libs/store", Local: true}) {
 		t.Errorf("after commit: %+v, want local change of libs/store", c)
 	}
 

internal/submodule/status.go

@@ -60,13 +60,14 @@ func (s *Status) Issues() []Issue {
 	return out
 }
 
-// Hidden counts issues below a submodule per level.
-type Hidden struct{ Warn, Danger int }
+// Hidden counts issues below a submodule per level, plus staged pins (which
+// are not issues).
+type Hidden struct{ Warn, Danger, Staged int }
 
-// Total is the number of issues of all levels.
+// Total is the number of issues of all levels; staged pins are not counted.
 func (h Hidden) Total() int { return h.Warn + h.Danger }
 
-// HiddenIssues counts the issues of all loaded descendants per level. A
+// HiddenIssues counts the issues and staged pins of all loaded descendants. A
 // descendant whose load failed counts as one danger, since its state is
 // unknown.
 func (m *Submodule) HiddenIssues() Hidden {
@@ -75,6 +76,9 @@ func (m *Submodule) HiddenIssues() Hidden {
 		if c.Status == nil && c.Err != nil {
 			h.Danger++
 		}
+		if c.Status != nil && c.Status.PinStaged {
+			h.Staged++
+		}
 		for _, is := range c.Status.Issues() {
 			switch is.Level {
 			case LevelDanger:

internal/submodule/status_test.go

@@ -39,15 +39,15 @@ func TestIssues(t *testing.T) {
 
 func TestHiddenIssues(t *testing.T) {
 	ok := &Status{Pin: PinInfo{Pushed: true}}
-	dirty := &Status{Worktree: WorktreeModified, Pin: PinInfo{Pushed: true}}
+	dirty := &Status{Worktree: WorktreeModified, Pin: PinInfo{Pushed: true}, PinStaged: true}
 	unpushed := &Status{}
 	grandchild := &Submodule{Status: unpushed}
 	child := &Submodule{Status: dirty, Children: []*Submodule{grandchild}}
 	loading := &Submodule{}
 	root := &Submodule{Status: ok, Children: []*Submodule{child, {Status: ok}, loading}}
 
-	if got := root.HiddenIssues(); got != (Hidden{Warn: 1, Danger: 1}) {
-		t.Errorf("HiddenIssues() = %+v; want 1 warn, 1 danger", got)
+	if got := root.HiddenIssues(); got != (Hidden{Warn: 1, Danger: 1, Staged: 1}) {
+		t.Errorf("HiddenIssues() = %+v; want 1 warn, 1 danger, 1 staged", got)
 	}
 }
 

internal/tui/app.go

@@ -4,10 +4,12 @@ package tui
 
 import (
 	"context"
+	"strings"
 	"time"
 
 	"github.com/charmbracelet/bubbles/key"
 	"github.com/charmbracelet/bubbles/spinner"
+	"github.com/charmbracelet/bubbles/textinput"
 	tea "github.com/charmbracelet/bubbletea"
 	"github.com/charmbracelet/lipgloss"
 	zone "github.com/lrstanley/bubblezone"
@@ -55,6 +57,10 @@ type Model struct {
 	detail  detail.Model
 	footer  footer.Model
 	spinner spinner.Model
+	filter  textinput.Model
+	// filtering is true while the filter line is shown; the filter applies
+	// exactly then. The input is focused while typing and blurred after enter.
+	filtering bool
 
 	width, height int
 	showDetail    bool
@@ -64,6 +70,12 @@ func New(ctx context.Context, p submodule.Provider, opts Options) Model {
 	t := theme.Default()
 	k := defaultKeys()
 	sp := spinner.New(spinner.WithSpinner(spinner.MiniDot))
+	fi := textinput.New()
+	fi.Prompt = "/ "
+	fi.PromptStyle = theme.Fg(t.Primary)
+	fi.Cursor.Style = theme.Fg(t.Primary)
+	fi.Placeholder = "filter by name or path"
+	fi.PlaceholderStyle = theme.Fg(t.Muted)
 	m := Model{
 		ctx:      ctx,
 		provider: p,
@@ -76,6 +88,7 @@ func New(ctx context.Context, p submodule.Provider, opts Options) Model {
 		detail:   detail.New(t, k.Submodule()),
 		footer:   footer.New(t, k),
 		spinner:  sp,
+		filter:   fi,
 	}
 	m.fetcher, _ = p.(submodule.Fetcher)
 	m.watcher, _ = p.(submodule.Watcher)
@@ -309,7 +322,12 @@ func (m Model) changed(msg changeMsg) (tea.Model, tea.Cmd) {
 
 func (m Model) handleKey(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 	k := m.keys
+	if m.filter.Focused() {
+		return m.typeFilter(msg)
+	}
 	switch {
+	case m.filtering && msg.Type == tea.KeyEsc:
+		m.closeFilter()
 	case key.Matches(msg, k.Quit):
 		return m, tea.Quit
 	case key.Matches(msg, k.Help):
@@ -355,7 +373,11 @@ func (m Model) handleKey(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 		return m, m.reloadTree(true)
 	case key.Matches(msg, k.Copy):
 		return m.copyPath()
-	case key.Matches(msg, k.Update, k.Bump, k.Filter, k.Issues):
+	case key.Matches(msg, k.Filter):
+		m.filtering = true
+		m.layout()
+		return m, m.filter.Focus()
+	case key.Matches(msg, k.Update, k.Bump, k.Issues):
 		cmd := m.footer.Flash("“" + msg.String() + "” is not implemented in the prototype")
 		m.layout()
 		return m, cmd
@@ -363,6 +385,57 @@ func (m Model) handleKey(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 	return m, nil
 }
 
+// typeFilter handles a key while the filter input has the focus: text edits
+// the filter, enter hands the keys back to the tree (the filter stays), esc
+// closes the filter. Arrows still move the selection.
+func (m Model) typeFilter(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
+	switch msg.Type {
+	case tea.KeyCtrlC:
+		return m, tea.Quit
+	case tea.KeyEsc:
+		m.closeFilter()
+	case tea.KeyEnter:
+		m.filter.Blur()
+	case tea.KeyUp:
+		m.tree.Up()
+	case tea.KeyDown:
+		m.tree.Down()
+	case tea.KeyPgUp:
+		m.tree.PageUp()
+	case tea.KeyPgDown:
+		m.tree.PageDown()
+	default:
+		var cmd tea.Cmd
+		m.filter, cmd = m.filter.Update(msg)
+		m.tree.SetFilter(m.filter.Value())
+		return m, cmd
+	}
+	return m, nil
+}
+
+// closeFilter hides the filter line and removes the filter; the selection stays.
+func (m *Model) closeFilter() {
+	m.filtering = false
+	m.filter.Blur()
+	m.filter.Reset()
+	m.tree.SetFilter("")
+	m.layout()
+}
+
+// filterView is the line above the footer: the input and, right-aligned, the
+// keys that apply.
+func (m Model) filterView() string {
+	hint := "enter navigate • esc close"
+	if !m.filter.Focused() {
+		hint = "/ edit • esc close"
+	}
+	hint = theme.Fg(m.theme.Muted).Render(hint)
+	m.filter.Width = max(m.width-lipgloss.Width(hint)-6, 1)
+	in := m.filter.View()
+	gap := max(m.width-2-lipgloss.Width(in)-lipgloss.Width(hint), 1)
+	return lipgloss.NewStyle().Width(m.width).Padding(0, 1).Render(in + strings.Repeat(" ", gap) + hint)
+}
+
 // copyPath copies the absolute directory of the selected submodule to the
 // clipboard, or its path in the superproject if the provider can't tell.
 func (m Model) copyPath() (tea.Model, tea.Cmd) {
@@ -384,7 +457,11 @@ func (m Model) copyPath() (tea.Model, tea.Cmd) {
 // layout distributes the terminal size among the components.
 func (m *Model) layout() {
 	m.footer.SetWidth(m.width)
-	bodyHeight := max(m.height-headerHeight-lipgloss.Height(m.footer.View()), 0)
+	bodyHeight := m.height - headerHeight - lipgloss.Height(m.footer.View())
+	if m.filtering {
+		bodyHeight--
+	}
+	bodyHeight = max(bodyHeight, 0)
 
 	m.showDetail = m.width >= detailHideBelow
 	treeWidth := m.width
@@ -415,9 +492,9 @@ func (m Model) View() string {
 		body = lipgloss.JoinHorizontal(lipgloss.Top, body, pane)
 	}
 
-	return zone.Scan(lipgloss.JoinVertical(lipgloss.Left,
-		header.View(m.theme, m.repo, m.fetch, m.spinner.View(), m.width),
-		body,
-		m.footer.View(),
-	))
+	parts := []string{header.View(m.theme, m.repo, m.fetch, m.spinner.View(), m.width), body}
+	if m.filtering {
+		parts = append(parts, m.filterView())
+	}
+	return zone.Scan(lipgloss.JoinVertical(lipgloss.Left, append(parts, m.footer.View())...))
 }

internal/tui/detail/detail.go

@@ -97,11 +97,11 @@ func (m Model) lines(s *submodule.Submodule) []string {
 	for _, is := range issues {
 		out = append(out, t.LevelStyle(is.Level, lipgloss.NewStyle()).Width(labelWidth).Render(theme.IssueWord(is.Kind))+text.Render(is.Detail))
 	}
-	if len(issues) == 0 {
+	if len(issues) == 0 && !st.PinStaged {
 		out = append(out, label(theme.InSync)+muted.Render("nothing to do"))
 	}
 	if st.PinStaged {
-		out = append(out, theme.Fg(t.Info).Width(labelWidth).Render("staged")+text.Render("pin change staged, not committed"))
+		out = append(out, theme.Fg(t.Info).Width(labelWidth).Render(theme.Staged)+text.Render("pin change staged, not committed"))
 	}
 	if st.Checkout == submodule.CheckoutDetached {
 		out = append(out, label("")+muted.Render("detached HEAD on pin"))
@@ -170,6 +170,9 @@ func (m Model) lines(s *submodule.Submodule) []string {
 		if h.Warn > 0 {
 			parts = append(parts, t.LevelStyle(submodule.LevelWarn, lipgloss.NewStyle()).Render(fmt.Sprintf("%d warning(s)", h.Warn)))
 		}
+		if h.Staged > 0 {
+			parts = append(parts, theme.Fg(t.Info).Render(fmt.Sprintf("%d %s", h.Staged, theme.Staged)))
+		}
 		if len(parts) > 0 {
 			children += muted.Render(" · ") + strings.Join(parts, muted.Render(", ")) + muted.Render(" below")
 		}

internal/tui/theme/issues.go

@@ -12,6 +12,10 @@ import (
 // InSync is the word for a submodule without issues.
 const InSync = "in sync"
 
+// Staged is the word for a pin change staged in the superproject. It is not
+// an issue: it replaces InSync, or follows an issue word as a marker.
+const Staged = "staged"
+
 // IssueWord is the short label for an issue kind shown in the tree.
 func IssueWord(k submodule.IssueKind) string {
 	switch k {

internal/tui/tree/filter.go

@@ -0,0 +1,141 @@
+package tree
+
+import (
+	"strings"
+
+	"submarine/internal/submodule"
+)
+
+// SetFilter shows only the submodules whose path contains term (ignoring
+// case), plus their ancestors, which are shown expanded. An empty term
+// removes the filter.
+//
+// If the selected submodule is filtered out, the next visible one is
+// selected (the previous one if there is none after it, none if nothing
+// matches). Removing the filter keeps the selection visible by expanding its
+// ancestors.
+func (m *Model) SetFilter(term string) {
+	term = strings.ToLower(term)
+	if term == m.filter {
+		return
+	}
+	old := m.cursor
+	m.filter = term
+	if term == "" {
+		for p := parentOf(old); p != nil; p = p.Parent {
+			m.expanded[p.Path] = true
+		}
+		if m.cursor == nil {
+			m.cursor = m.firstNode()
+		}
+	} else {
+		m.reselect(old)
+	}
+	m.clampOffset()
+}
+
+// Filter returns the active filter term in lower case.
+func (m Model) Filter() string { return m.filter }
+
+func parentOf(s *submodule.Submodule) *submodule.Submodule {
+	if s == nil {
+		return nil
+	}
+	return s.Parent
+}
+
+// reselect makes sure the cursor is on a visible submodule. If old is not
+// visible any more, the closest visible one after it in display order
+// becomes the selection, else the closest one before it.
+func (m *Model) reselect(old *submodule.Submodule) {
+	visible := map[*submodule.Submodule]bool{}
+	var first *submodule.Submodule
+	for _, r := range m.rows() {
+		if r.kind == rowNode {
+			visible[r.node] = true
+			if first == nil {
+				first = r.node
+			}
+		}
+	}
+	if old != nil && visible[old] {
+		m.cursor = old
+		return
+	}
+	m.cursor = first
+	if old == nil || first == nil {
+		return
+	}
+	var all []row
+	m.appendAll(&all, m.roots, 0)
+	i := 0
+	for ; i < len(all); i++ {
+		if all[i].node == old {
+			break
+		}
+	}
+	for j := i + 1; j < len(all); j++ {
+		if visible[all[j].node] {
+			m.cursor = all[j].node
+			return
+		}
+	}
+	for j := i - 1; j >= 0; j-- {
+		if visible[all[j].node] {
+			m.cursor = all[j].node
+			return
+		}
+	}
+}
+
+// appendAll lists every submodule in display order, whatever is expanded or
+// filtered.
+func (m *Model) appendAll(out *[]row, mods []*submodule.Submodule, depth int) {
+	for _, g := range groupByDir(mods) {
+		for _, s := range g.mods {
+			*out = append(*out, row{kind: rowNode, depth: depth, node: s})
+			m.appendAll(out, s.Children, depth+1)
+		}
+	}
+}
+
+// isExpanded reports whether the children of s are shown. While filtering,
+// that is the case if a match is below s, whatever the user expanded.
+func (m *Model) isExpanded(s *submodule.Submodule) bool {
+	if m.filter == "" {
+		return m.expanded[s.Path]
+	}
+	for _, c := range s.Children {
+		if m.shown(c) {
+			return true
+		}
+	}
+	return false
+}
+
+// filtered returns the submodules of mods that pass the filter.
+func (m *Model) filtered(mods []*submodule.Submodule) []*submodule.Submodule {
+	if m.filter == "" {
+		return mods
+	}
+	var out []*submodule.Submodule
+	for _, s := range mods {
+		if m.shown(s) {
+			out = append(out, s)
+		}
+	}
+	return out
+}
+
+// shown reports whether s matches the filter or has a descendant that does.
+func (m *Model) shown(s *submodule.Submodule) bool {
+	if strings.Contains(strings.ToLower(s.Path), m.filter) {
+		return true
+	}
+	for _, c := range s.Children {
+		if m.shown(c) {
+			return true
+		}
+	}
+	return false
+}

internal/tui/tree/rows.go

@@ -30,7 +30,7 @@ func (m *Model) rows() []row {
 // appendRows groups mods by the directory of their RelPath. Each group with a
 // directory gets a header row; its submodules are indented one level deeper.
 func (m *Model) appendRows(out *[]row, mods []*submodule.Submodule, depth int) {
-	for _, g := range groupByDir(mods) {
+	for _, g := range groupByDir(m.filtered(mods)) {
 		d := depth
 		if g.dir != "." {
 			*out = append(*out, row{kind: rowDir, depth: depth, label: g.dir + "/"})
@@ -38,7 +38,7 @@ func (m *Model) appendRows(out *[]row, mods []*submodule.Submodule, depth int) {
 		}
 		for _, s := range g.mods {
 			*out = append(*out, row{kind: rowNode, depth: d, node: s})
-			if m.expanded[s.Path] && len(s.Children) > 0 {
+			if m.isExpanded(s) && len(s.Children) > 0 {
 				m.appendRows(out, s.Children, d+1)
 			}
 		}

internal/tui/tree/tree.go

@@ -25,6 +25,7 @@ type Model struct {
 	theme    theme.Theme
 	roots    []*submodule.Submodule
 	expanded map[string]bool // keyed by Submodule.Path; kept when ancestors collapse
+	filter   string          // lower-case; empty if not filtering
 	cursor   *submodule.Submodule
 	offset   int // index of the first visible row
 	width    int
@@ -42,9 +43,7 @@ func (m *Model) SetRoots(roots []*submodule.Submodule) {
 	m.expanded = map[string]bool{}
 	m.cursor = nil
 	m.offset = 0
-	if len(roots) > 0 {
-		m.cursor = m.rows()[m.firstNodeRow()].node
-	}
+	m.cursor = m.firstNode()
 }
 
 // ReplaceRoots swaps in a reloaded tree. Unlike SetRoots it keeps the
@@ -63,8 +62,8 @@ func (m *Model) ReplaceRoots(roots []*submodule.Submodule) {
 			break
 		}
 	}
-	if m.cursor == nil && len(roots) > 0 {
-		m.cursor = m.rows()[m.firstNodeRow()].node
+	if m.cursor == nil {
+		m.reselect(nil)
 	}
 	m.clampOffset()
 }
@@ -210,6 +209,15 @@ func (m Model) cursorRow(rows []row) int {
 	return -1
 }
 
+func (m *Model) firstNode() *submodule.Submodule {
+	for _, r := range m.rows() {
+		if r.kind == rowNode {
+			return r.node
+		}
+	}
+	return nil
+}
+
 func (m Model) firstNodeRow() int {
 	for i, r := range m.rows() {
 		if r.kind == rowNode {
@@ -304,6 +312,9 @@ func (m Model) View() string {
 			lines = append(lines, m.nodeLine(r, nameColW, refW))
 		}
 	}
+	if len(rows) == 0 && m.filter != "" {
+		lines = append(lines, theme.Fg(m.theme.Muted).Width(m.width).Render(" no submodule matches"))
+	}
 	for len(lines) < m.height {
 		lines = append(lines, strings.Repeat(" ", m.width))
 	}
@@ -324,7 +335,7 @@ func (m Model) nameColumnWidth(rows []row, refW int) int {
 }
 
 func (m Model) childCount(s *submodule.Submodule) string {
-	if len(s.Children) == 0 || m.expanded[s.Path] {
+	if len(s.Children) == 0 || m.isExpanded(s) {
 		return ""
 	}
 	return fmt.Sprintf(" [%d]", len(s.Children))
@@ -368,7 +379,7 @@ func (m Model) nodeLine(r row, nameColW, refW int) string {
 	}
 	pad := func(n int) string { return base.Render(strings.Repeat(" ", max(n, 0))) }
 
-	collapsed := len(s.Children) > 0 && !m.expanded[s.Path]
+	collapsed := len(s.Children) > 0 && !m.isExpanded(s)
 
 	// toggle marker
 	marker := "  "
@@ -399,7 +410,12 @@ func (m Model) nodeLine(r row, nameColW, refW int) string {
 	nameCell := seg(textColor, name) + seg(t.Muted, count) + pad(nameW-lipgloss.Width(name+count))
 
 	// status: the most severe issue as a word, "+n" for further issues;
-	// a muted "in sync" without issues, so an empty cell never looks broken
+	// a muted "in sync" without issues, so an empty cell never looks broken.
+	// A staged pin is no issue: it replaces "in sync", or follows the issue
+	// as a blue marker (also for staged pins below a collapsed row).
+	staged := s.Status != nil && s.Status.PinStaged
+	h := s.HiddenIssues()
+	stagedMark := staged && len(issues) > 0
 	var status string
 	switch {
 	case s.Err != nil:
@@ -411,10 +427,15 @@ func (m Model) nodeLine(r row, nameColW, refW int) string {
 		if len(issues) > 1 {
 			status += seg(t.Muted, fmt.Sprintf(" +%d", len(issues)-1))
 		}
+	case staged:
+		status = seg(t.Info, theme.Staged)
 	default:
 		status = seg(t.Muted, theme.InSync)
 	}
-	if h := s.HiddenIssues(); collapsed && h.Total() > 0 {
+	if stagedMark || collapsed && h.Staged > 0 {
+		status += pad(1) + seg(t.Info, t.Glyphs.Staged)
+	}
+	if collapsed && h.Total() > 0 {
 		for _, c := range []struct {
 			level submodule.Level
 			n     int

internal/tui/tree/tree_test.go

@@ -249,3 +249,59 @@ func TestExpandAllOnLeafKeepsSelection(t *testing.T) {
 		t.Fatal("all nodes with children should be expanded")
 	}
 }
+
+func TestFilterShowsMatchesWithAncestors(t *testing.T) {
+	m := newTree(t)
+	m.SetFilter("D")
+	want := []string{"src/", "b", "modules/", "c", "d"}
+	if got := visible(m); !equal(got, want) {
+		t.Fatalf("rows = %v, want %v", got, want)
+	}
+	assertCursor(t, m, "b") // a was selected and is gone: next available (an ancestor of the match)
+}
+
+func TestFilterSelectionMovesToNextThenPrevious(t *testing.T) {
+	m := newTree(t)
+	m.Select("a")
+	m.SetFilter("f")
+	assertCursor(t, m, "f")
+	m.SetFilter("")
+	m.Select("f")
+	m.SetFilter("a") // only a matches, it lies before f
+	assertCursor(t, m, "a")
+}
+
+func TestFilterWithoutMatchSelectsNothing(t *testing.T) {
+	m := newTree(t)
+	m.SetFilter("zzz")
+	if m.Selected() != nil || len(m.rows()) != 0 {
+		t.Fatalf("selected %v, rows %v", m.Selected(), visible(m))
+	}
+	m.Down() // must not panic
+	m.SetFilter("f")
+	assertCursor(t, m, "f")
+}
+
+func TestClearingFilterKeepsSelectionVisible(t *testing.T) {
+	m := newTree(t)
+	m.SetFilter("d")
+	m.Select("d")
+	m.SetFilter("")
+	assertCursor(t, m, "d")
+	want := []string{"a", "src/", "b", "modules/", "c", "d", "e", "f"}
+	if got := visible(m); !equal(got, want) {
+		t.Fatalf("rows = %v, want %v", got, want)
+	}
+}
+
+func equal(a, b []string) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i := range a {
+		if a[i] != b[i] {
+			return false
+		}
+	}
+	return true
+}