Add / filter for the tree

A text input above the footer filters submodules by path (case-insensitive).
Matches keep their ancestors. A filtered-out selection moves to the next
visible submodule; esc closes the input and removes the filter.

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

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/architecture.md

@@ -31,7 +31,7 @@ internal/tui/                 Bubble Tea application
   tree/                       tree component: rows, navigation, mouse, view
   detail/                     detail pane; changes.go: change preview
   header/                     header line
-  footer/                     help and flash messages
+  footer/                     key bar (navigation left, global right) and flash messages
 ```
 
 ### Layering rules
@@ -64,6 +64,12 @@ type Watcher interface {
 }
 ```
 
+```go
+type Locator interface {
+    Dir(path string) string                    // absolute directory, "" if unknown
+}
+```
+
 - `Tree` returns the superproject and all submodules with `Parent` and
   `Children` linked. `Status` fields are nil.
 - `Status` is called once per submodule, concurrently. It must be safe to

docs/decisions.md

@@ -7,7 +7,8 @@ Each entry: context, decision, consequences. Newest last.
 **Context.** Hashes don't tell users whether a pin is current.
 **Decision.** Resolve each pin to a ref and show the distance (`origin/main ↓1`).
 The resolution order is fixed and the applied rule is shown in the detail pane
-(see [state-model.md](state-model.md#resolving-a-pin-to-a-ref)).
+(see [state-model.md](state-model.md#resolving-a-pin-to-a-ref); amended:
+the closest branch wins, see "Pin resolves to the closest branch").
 **Consequences.** Resolution is a heuristic; showing the rule keeps it
 transparent.
 
@@ -200,3 +201,48 @@ package so versions stay clean.
 corrupt or partial downloads, not a compromised registry (no signatures).
 The update check is a deliberate, outside-the-provider network use: only
 on `update` and a once-a-day background check that can be disabled.
+
+## Copy path with `c` via OSC 52
+
+`c` copies the selected submodule's absolute directory (optional
+`submodule.Locator`; the relative path as fallback). The absolute path is
+what a shell needs (`cd <paste>`). OSC 52 instead of a clipboard tool
+(`xclip`, `pbcopy`): no external dependency and it works over SSH. The cost:
+terminals that block OSC 52 copy nothing silently; the footer still says
+`copied`, since the application can't know.
+
+## Key groups: global, navigation, submodule
+
+Keys that act on the selected submodule (copy path, later checkout, bump) are
+shown in a palette in the detail pane, next to what they act on; global keys
+(`?`, `q`) sit right in the footer. Where the pane can't show the palette
+(hidden below 90 columns, or under 12 lines) the footer shows these keys
+instead, so small terminals need no extra UI (no overlay or action menu).
+Keys never depend on what is visible.
+
+## Pin resolves to the closest branch
+
+A pin on a pushed feature branch showed as diverged from `origin/main`,
+because `branch = main` in `.gitmodules` won before any distance was looked
+at. Now the closest branch containing the pin wins; the `.gitmodules`
+branch, the upstream and the remote default branch only break ties (and are
+always compared, even past the 16-branch cap). An unpushed pin compares only
+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).

docs/requirements.md

@@ -103,13 +103,18 @@ 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

@@ -104,17 +104,30 @@ A descendant whose load failed (`error`) counts as one danger.
 ## Resolving a pin to a ref
 
 The pin is displayed as a ref, not a hash. A commit can be on several
-branches, on none, or deep in the history, so the git provider resolves it by
+branches, on none, or deep in the history. The git provider shows the
-this order and records which rule applied in `PinInfo.Source`:
+**closest** branch and records which rule proposed it in `PinInfo.Source`.
+
+Preferred refs, in this order (each only if it exists):
+
+| Preference | Ref | `RefSource` |
+|---|---|---|
+| a | `branch = …` in `.gitmodules` | `RefFromGitmodules` |
+| b | Upstream of the branch checked out in the submodule | `RefFromCurrentBranch` |
+| c | Remote default branch (`<remote>/HEAD`) | `RefFromDefaultBranch` |
+
+Resolution:
 
 | # | Rule | `RefSource` |
 |---|---|---|
-| 1 | `branch = …` in `.gitmodules` | `RefFromGitmodules` |
+| 1 | Pin pushed: the branch containing the pin with the fewest commits after it. Candidates are the preferred refs that contain the pin plus any remote branch containing it (`for-each-ref --contains`); a tie goes to the preferred ref | preferred ref's, else `RefFromContains` |
-| 2 | Branch currently checked out in the submodule | `RefFromCurrentBranch` |
+| 2 | Pin unpushed: the preferred ref with the fewest commits on either side (`↑n↓m`), ties by preference | preferred ref's |
-| 3 | Remote default branch, if it contains the pin | `RefFromDefaultBranch` |
+| 3 | A tag (`git describe`) | `RefFromTag` |
-| 4 | Any remote branch containing the pin, preferring the closest tip (`git branch -r --contains`) | `RefFromContains` |
+| 4 | Short SHA | `RefFromSHA` |
-| 5 | A tag (`git describe`) | `RefFromTag` |
+
-| 6 | Short SHA | `RefFromSHA` |
+So a `.gitmodules` branch is shown when it is as close as any other branch,
+but a pin that sits on a feature branch shows that branch rather than
+"diverged from main". The trade-off: a pin on main that a younger branch
+also contains shows the younger branch if its tip is fewer commits away.
 
 Distances: `git rev-list --left-right --count <pin>...<ref>` gives
 `Ahead` (left) and `Behind` (right).
@@ -143,12 +156,13 @@ are local; `<pin>` is the index gitlink.
 
 Details:
 
-- Rule 1: `branch = .` means the superproject's current branch. The rule
+- Preference a: `branch = .` means the superproject's current branch. The
-  applies only if `<remote>/<branch>` exists locally.
+  ref counts only if `<remote>/<branch>` exists locally.
-- Rule 2 uses the checked-out branch's upstream (`<branch>@{upstream}`).
+- Preference b uses the checked-out branch's upstream (`<branch>@{upstream}`).
-- Rule 4 compares at most 16 containing branches (oldest tip first) and
+- Rule 1 counts `rev-list --count <pin>..<ref>`. Besides the preferred refs
-  picks the one with the fewest commits after the pin.
+  it compares at most 16 containing branches (oldest tip first).
-- Rule 6 shows the short SHA; there is no tip and no distance.
+- Rule 2 counts `rev-list --count <pin>...<ref>`.
+- Rule 4 shows the short SHA; there is no tip and no distance.
 - `--ignore-submodules=dirty`: changes inside a nested submodule do not make
   its parent `changed` (D7), but a moved nested pin does.
 - Renames are detected only for staged moves (`git mv`); an unstaged move

docs/ux-guide.md

@@ -34,8 +34,24 @@
 | 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
+
+Keys come in three groups (`keyMap.Navigation`, `.Submodule`, `.Global`):
+
+- **Navigation** (move, fold, toggle): left in the footer.
+- **Global** (`?`, `q`): right-aligned in the footer, always kept.
+- **Submodule** (act on the selected one, e.g. `c`): a palette on the last
+  line of the detail pane. It is left out if the pane is shorter than 12
+  lines. Whenever the palette isn't shown (pane hidden or too short), these
+  keys move into the footer after the navigation keys.
+
+If the footer is too narrow, keys are dropped from the left group's end
+(submodule keys first); the global keys stay. Full help (`?`) lists all keys
+in columns, whatever the size. Keys work whether or not they are shown.
+
 ### Tree row
 
 ```
@@ -191,7 +207,9 @@ colors in components.
 | `q`, `ctrl+c` | Quit |
 | `f` | Fetch all repositories (does nothing while a fetch runs) |
 | `r` | Reload everything (e.g. after editing files) |
-| `u`, `b`, `/`, `!` | Planned actions (see requirements) |
+| `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 |
+| `/` | 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).
@@ -200,6 +218,52 @@ 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
+table when a key is added, moved or implemented. "Bar" is the short footer
+bar, "Palette" the detail pane's palette (the footer takes its keys over
+where the palette can't be shown, see [Key bar and palette](#key-bar-and-palette)),
+"Help" the full help (`?`).
+
+| Key | Action | Group | Shown in | Implemented |
+|---|---|---|---|---|
+| `↑` / `k`, `↓` / `j` | Move selection | Navigation | Bar, Help | yes |
+| `←` / `h`, `→` / `l` | Fold / unfold, parent / first child | Navigation | Bar, Help | yes |
+| `H` / `⇧←`, `L` / `⇧→` | Collapse / expand all | Navigation | Bar, Help | yes |
+| `space` | Toggle expand/collapse | Navigation | Bar, Help | yes |
+| `home` / `g`, `end` / `G` | First / last submodule | Navigation | Help | yes |
+| `pgup`, `pgdn` | Move by one screen | Navigation | Help | yes |
+| `c` | Copy path | Submodule | Palette, Help | yes |
+| `u` | Checkout pin | Submodule | Help | no (flashes "not implemented") |
+| `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 | yes |
+| `!` | Problems only | Global | Help | no (flashes "not implemented") |
+| `?` | Toggle full help | Global | Bar, Help | yes |
+| `q`, `ctrl+c` | Quit | Global | Bar, Help | yes |
+
 ### Mouse
 
 - Click a row: select it.

go.mod

@@ -3,6 +3,7 @@ module submarine
 go 1.27.3
 
 require (
+	github.com/aymanbagabas/go-osc52/v2 v2.0.1
 	github.com/charmbracelet/bubbles v1.0.0
 	github.com/charmbracelet/bubbletea v1.3.10
 	github.com/charmbracelet/lipgloss v1.1.0
@@ -11,7 +12,7 @@ require (
 )
 
 require (
-	github.com/aymanbagabas/go-osc52/v2 v2.0.1 // indirect
+	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.go

@@ -36,6 +36,17 @@ func (p *Provider) Fetchable(path string) bool {
 	return ok
 }
 
+// Dir returns the absolute directory of path ("" is the superproject),
+// whether or not it is initialized.
+func (p *Provider) Dir(path string) string {
+	if path == "" {
+		return p.root
+	}
+	p.mu.RLock()
+	defer p.mu.RUnlock()
+	return p.mods[path].dir
+}
+
 // repoDir returns the worktree of path if it is initialized.
 func (p *Provider) repoDir(path string) (string, bool) {
 	if path == "" {

internal/submodule/git/provider.go

@@ -20,7 +20,7 @@ import (
 )
 
 // maxContainsCandidates limits how many remote branches containing the pin
-// are compared when resolving the pin by RefFromContains.
+// are compared besides the preferred refs when resolving a pushed pin.
 const maxContainsCandidates = 16
 
 // maxBetween limits the commits listed between pin and tip.
@@ -269,80 +269,130 @@ func status(ctx context.Context, in info) (*submodule.Status, error) {
 }
 
 // resolve finds the ref that describes the pin, following the order in
-// docs/state-model.md. containing lists the remote branches containing the
+// docs/state-model.md: the closest branch wins, the preferred refs (see
-// pin, oldest tip first.
+// preferredRefs) break ties. containing lists the remote branches containing
+// the pin, oldest tip first.
 func resolve(ctx context.Context, in info, pin, branch string, containing []string) (string, submodule.RefSource, error) {
-	remote, err := remoteName(ctx, in.dir)
+	preferred, err := preferredRefs(ctx, in, branch)
 	if err != nil {
 		return "", 0, err
 	}
 
-	// 1. branch from .gitmodules
+	// 1. pushed: the branch containing the pin with the fewest commits after it
-	if b := in.branch; b != "" && remote != "" {
+	if len(containing) > 0 {
-		if b == "." {
+		var cands []candidate
-			b, _, err = try(ctx, in.superDir, "symbolic-ref", "--short", "-q", "HEAD")
+		for _, c := range preferred {
-			if err != nil {
+			if _, ok, err := try(ctx, in.dir, "merge-base", "--is-ancestor", pin, c.ref); err != nil {
-				return "", 0, err
-			}
-		}
-		if b != "" {
-			if _, ok, err := try(ctx, in.dir, "rev-parse", "--verify", "-q", "refs/remotes/"+remote+"/"+b); err != nil {
 				return "", 0, err
 			} else if ok {
-				return remote + "/" + b, submodule.RefFromGitmodules, nil
+				cands = append(cands, c)
 			}
 		}
-	}
-
-	// 2. upstream of the checked-out branch
-	if branch != "" {
-		if up, ok, err := try(ctx, in.dir, "rev-parse", "--abbrev-ref", "--symbolic-full-name", branch+"@{upstream}"); err != nil {
-			return "", 0, err
-		} else if ok && up != "" {
-			return up, submodule.RefFromCurrentBranch, nil
-		}
-	}
-
-	// 3. remote default branch, if it contains the pin
-	if remote != "" {
-		if def, ok, err := try(ctx, in.dir, "symbolic-ref", "--short", "-q", "refs/remotes/"+remote+"/HEAD"); err != nil {
-			return "", 0, err
-		} else if ok {
-			if _, ok, err := try(ctx, in.dir, "merge-base", "--is-ancestor", pin, def); err != nil {
-				return "", 0, err
-			} else if ok {
-				return def, submodule.RefFromDefaultBranch, nil
-			}
-		}
-	}
-
-	// 4. remote branch containing the pin with the closest tip
-	best, bestN := "", -1
 		for _, r := range containing[:min(len(containing), maxContainsCandidates)] {
-		out, err := run(ctx, in.dir, "rev-list", "--count", pin+".."+r)
+			if !slices.ContainsFunc(cands, func(c candidate) bool { return c.ref == r }) {
-		if err != nil {
+				cands = append(cands, candidate{r, submodule.RefFromContains})
+			}
+		}
+		if c, ok, err := closest(ctx, in.dir, pin+"..", cands); err != nil {
 			return "", 0, err
+		} else if ok {
+			return c.ref, c.source, nil
 		}
-		var n int
-		if _, err := fmt.Sscan(out, &n); err == nil && (bestN < 0 || n < bestN) {
-			best, bestN = r, n
-		}
-	}
-	if best != "" {
-		return best, submodule.RefFromContains, nil
 	}
 
-	// 5. nearest tag
+	// 2. unpushed: the preferred ref with the fewest commits on either side
+	if c, ok, err := closest(ctx, in.dir, pin+"...", preferred); err != nil {
+		return "", 0, err
+	} else if ok {
+		return c.ref, c.source, nil
+	}
+
+	// 3. nearest tag
 	if tag, ok, err := try(ctx, in.dir, "describe", "--tags", "--abbrev=0", pin); err != nil {
 		return "", 0, err
 	} else if ok && tag != "" {
 		return tag, submodule.RefFromTag, nil
 	}
 
-	// 6. the commit itself
+	// 4. the commit itself
 	return "", submodule.RefFromSHA, nil
 }
 
+// candidate is a ref the pin may resolve to and the rule that proposed it.
+type candidate struct {
+	ref    string
+	source submodule.RefSource
+}
+
+// preferredRefs returns the refs the user most likely means, in order of
+// preference and without duplicates: the .gitmodules branch, the upstream of
+// the checked-out branch, the remote default branch. Each must exist.
+func preferredRefs(ctx context.Context, in info, branch string) ([]candidate, error) {
+	remote, err := remoteName(ctx, in.dir)
+	if err != nil {
+		return nil, err
+	}
+	var refs []candidate
+	add := func(ref string, source submodule.RefSource) {
+		if ref != "" && !slices.ContainsFunc(refs, func(c candidate) bool { return c.ref == ref }) {
+			refs = append(refs, candidate{ref, source})
+		}
+	}
+
+	// branch from .gitmodules
+	if b := in.branch; b != "" && remote != "" {
+		if b == "." {
+			b, _, err = try(ctx, in.superDir, "symbolic-ref", "--short", "-q", "HEAD")
+			if err != nil {
+				return nil, err
+			}
+		}
+		if b != "" {
+			if _, ok, err := try(ctx, in.dir, "rev-parse", "--verify", "-q", "refs/remotes/"+remote+"/"+b); err != nil {
+				return nil, err
+			} else if ok {
+				add(remote+"/"+b, submodule.RefFromGitmodules)
+			}
+		}
+	}
+
+	// upstream of the checked-out branch
+	if branch != "" {
+		if up, ok, err := try(ctx, in.dir, "rev-parse", "--abbrev-ref", "--symbolic-full-name", branch+"@{upstream}"); err != nil {
+			return nil, err
+		} else if ok {
+			add(up, submodule.RefFromCurrentBranch)
+		}
+	}
+
+	// remote default branch
+	if remote != "" {
+		if def, ok, err := try(ctx, in.dir, "symbolic-ref", "--short", "-q", "refs/remotes/"+remote+"/HEAD"); err != nil {
+			return nil, err
+		} else if ok {
+			add(def, submodule.RefFromDefaultBranch)
+		}
+	}
+	return refs, nil
+}
+
+// closest returns the candidate with the fewest commits in the range
+// `<from><ref>` (from is e.g. "<pin>.."); the first one wins a tie.
+func closest(ctx context.Context, dir, from string, cands []candidate) (candidate, bool, error) {
+	best, bestN := candidate{}, -1
+	for _, c := range cands {
+		out, err := run(ctx, dir, "rev-list", "--count", from+c.ref)
+		if err != nil {
+			return candidate{}, false, err
+		}
+		var n int
+		if _, err := fmt.Sscan(out, &n); err == nil && (bestN < 0 || n < bestN) {
+			best, bestN = c, n
+		}
+	}
+	return best, bestN >= 0, nil
+}
+
 // remoteName returns "origin" if it exists, else the first remote, else "".
 func remoteName(ctx context.Context, dir string) (string, error) {
 	out, err := run(ctx, dir, "remote")

internal/submodule/git/provider_test.go

@@ -75,7 +75,7 @@ func TestTree(t *testing.T) {
 	submodule.Walk(repo.Submodules, func(s *submodule.Submodule) { paths = append(paths, s.Path) })
 	want := []string{
 		"src/core", "src/ui", "src/net", "libs/store", "libs/log", "libs/log/modules/nested",
-		"libs/feature", "libs/conflict", "libs/staged", "libs/missing", "vendor", "libs/work",
+		"libs/feature", "libs/conflict", "libs/staged", "libs/missing", "vendor", "libs/work", "libs/topic",
 	}
 	if !slices.Equal(paths, want) {
 		t.Errorf("paths = %v\nwant    %v", paths, want)
@@ -106,6 +106,7 @@ func TestStatus(t *testing.T) {
 		{path: "libs/log", ref: "origin/main", source: submodule.RefFromCurrentBranch},
 		{path: "libs/log/modules/nested", issues: []submodule.IssueKind{submodule.IssueChanged}, ref: "origin/main", source: submodule.RefFromDefaultBranch, checkout: submodule.CheckoutDetached},
 		{path: "libs/feature", ref: "origin/feat/search", source: submodule.RefFromContains, behind: 1, checkout: submodule.CheckoutDetached},
+		{path: "libs/topic", ref: "origin/feat/search", source: submodule.RefFromContains, checkout: submodule.CheckoutDetached},
 		{path: "libs/conflict", issues: []submodule.IssueKind{submodule.IssueConflict}, ref: "origin/main", source: submodule.RefFromCurrentBranch, staged: true},
 		{path: "libs/staged", ref: "origin/main", source: submodule.RefFromCurrentBranch, staged: true},
 		{path: "libs/missing", issues: []submodule.IssueKind{submodule.IssueMissing}},

internal/submodule/provider.go

@@ -26,6 +26,13 @@ type Watcher interface {
 	Watch(ctx context.Context) <-chan Change
 }
 
+// Locator is implemented by providers whose submodules live on the local
+// disk. Dir returns the absolute directory of path ("" is the superproject),
+// or "" if it is unknown.
+type Locator interface {
+	Dir(path string) string
+}
+
 // Change reports that the git metadata of a repository changed.
 type Change struct {
 	Path      string // "" is the superproject

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,
@@ -73,9 +85,10 @@ func New(ctx context.Context, p submodule.Provider, opts Options) Model {
 		loads:    newReloader(),
 		ticking:  true, // Init schedules the first tick
 		tree:     tree.New(t),
-		detail:   detail.New(t),
+		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):
@@ -353,7 +371,13 @@ func (m Model) handleKey(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 		return m, m.startFetch()
 	case key.Matches(msg, k.Reload):
 		return m, m.reloadTree(true)
-	case key.Matches(msg, k.Update, k.Bump, k.Filter, k.Issues):
+	case key.Matches(msg, k.Copy):
+		return m.copyPath()
+	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
@@ -361,10 +385,83 @@ 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) {
+	s := m.tree.Selected()
+	if s == nil {
+		return m, nil
+	}
+	path := s.Path
+	if l, ok := m.provider.(submodule.Locator); ok {
+		if dir := l.Dir(s.Path); dir != "" {
+			path = dir
+		}
+	}
+	cmd := tea.Batch(copyToClipboard(path), m.footer.Flash("copied "+path))
+	m.layout()
+	return m, 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
@@ -373,6 +470,7 @@ func (m *Model) layout() {
 		treeWidth = m.width - detailWidth
 		m.detail.SetSize(detailWidth-2, bodyHeight) // border + padding
 	}
+	m.footer.SetActions(!m.showDetail || !m.detail.PaletteVisible())
 	m.tree.SetSize(treeWidth, bodyHeight)
 }
 
@@ -394,9 +492,9 @@ func (m Model) View() string {
 		body = lipgloss.JoinHorizontal(lipgloss.Top, body, pane)
 	}
 
-	return zone.Scan(lipgloss.JoinVertical(lipgloss.Left,
+	parts := []string{header.View(m.theme, m.repo, m.fetch, m.spinner.View(), m.width), body}
-		header.View(m.theme, m.repo, m.fetch, m.spinner.View(), m.width),
+	if m.filtering {
-		body,
+		parts = append(parts, m.filterView())
-		m.footer.View(),
+	}
-	))
+	return zone.Scan(lipgloss.JoinVertical(lipgloss.Left, append(parts, m.footer.View())...))
 }

internal/tui/clipboard.go

@@ -0,0 +1,21 @@
+package tui
+
+import (
+	"os"
+
+	"github.com/aymanbagabas/go-osc52/v2"
+	tea "github.com/charmbracelet/bubbletea"
+)
+
+// copyToClipboard sets the system clipboard with the OSC 52 escape sequence,
+// which works over SSH and in terminals that allow it; others ignore it.
+func copyToClipboard(text string) tea.Cmd {
+	return func() tea.Msg {
+		seq := osc52.New(text)
+		if os.Getenv("TMUX") != "" {
+			seq = seq.Tmux()
+		}
+		_, _ = seq.WriteTo(os.Stderr)
+		return nil
+	}
+}

internal/tui/detail/detail.go

@@ -6,6 +6,8 @@ import (
 	"path"
 	"strings"
 
+	"github.com/charmbracelet/bubbles/help"
+	"github.com/charmbracelet/bubbles/key"
 	"github.com/charmbracelet/lipgloss"
 	"github.com/charmbracelet/x/ansi"
 
@@ -20,9 +22,20 @@ type Model struct {
 	width   int
 	height  int
 	spinner string
+	help    help.Model
+	actions []key.Binding
 }
 
-func New(t theme.Theme) Model { return Model{theme: t} }
+// paletteMinHeight is the pane height below which the palette is left out:
+// the information is worth more than the hints.
+const paletteMinHeight = 12
+
+func New(t theme.Theme, actions []key.Binding) Model {
+	return Model{theme: t, help: theme.NewHelp(t), actions: actions}
+}
+
+// PaletteVisible reports whether the palette of submodule actions fits.
+func (m Model) PaletteVisible() bool { return m.height >= paletteMinHeight }
 
 func (m *Model) SetSize(w, h int)        { m.width, m.height = w, h }
 func (m *Model) SetSpinner(frame string) { m.spinner = frame }
@@ -38,10 +51,21 @@ func (m Model) View(s *submodule.Submodule) string {
 	for i, l := range lines {
 		lines[i] = ansi.Truncate(l, m.width, "…")
 	}
-	if len(lines) > m.height {
+	height := m.height
-		lines = lines[:m.height]
+	var palette string
+	if m.PaletteVisible() {
+		height-- // the palette is the last line
+		m.help.Width = 0
+		palette = ansi.Truncate(m.help.ShortHelpView(m.actions), m.width, "…")
 	}
-	return lipgloss.NewStyle().Width(m.width).Height(m.height).Render(strings.Join(lines, "\n"))
+	if len(lines) > height {
+		lines = lines[:height]
+	}
+	body := lipgloss.NewStyle().Width(m.width).Height(height).Render(strings.Join(lines, "\n"))
+	if palette == "" {
+		return body
+	}
+	return body + "\n" + palette
 }
 
 func (m Model) lines(s *submodule.Submodule) []string {

internal/tui/footer/footer.go

@@ -2,11 +2,14 @@
 package footer
 
 import (
+	"strings"
 	"time"
 
 	"github.com/charmbracelet/bubbles/help"
+	"github.com/charmbracelet/bubbles/key"
 	tea "github.com/charmbracelet/bubbletea"
 	"github.com/charmbracelet/lipgloss"
+	"github.com/charmbracelet/x/ansi"
 
 	"submarine/internal/tui/theme"
 )
@@ -15,26 +18,34 @@ const flashDuration = 2 * time.Second
 
 type clearFlashMsg struct{ id int }
 
+// Keys provides the key groups. The short bar shows Navigation (and
+// Submodule, if requested) on the left and Global on the right; full help
+// shows FullHelp.
+type Keys interface {
+	help.KeyMap
+	Navigation() []key.Binding
+	Submodule() []key.Binding
+	Global() []key.Binding
+}
+
 type Model struct {
 	theme   theme.Theme
 	help    help.Model
-	keys    help.KeyMap
+	keys    Keys
 	width   int
 	flash   string
 	flashID int
+	actions bool // show the submodule bindings in the short bar
 }
 
-func New(t theme.Theme, keys help.KeyMap) Model {
+func New(t theme.Theme, keys Keys) Model {
-	h := help.New()
+	return Model{theme: t, help: theme.NewHelp(t), keys: keys}
-	h.Styles.ShortKey = theme.Fg(t.Text).Bold(true)
-	h.Styles.ShortDesc = theme.Fg(t.Muted)
-	h.Styles.ShortSeparator = theme.Fg(t.Border)
-	h.Styles.FullKey = h.Styles.ShortKey
-	h.Styles.FullDesc = h.Styles.ShortDesc
-	h.Styles.FullSeparator = h.Styles.ShortSeparator
-	return Model{theme: t, help: h, keys: keys}
 }
 
+// SetActions shows the submodule bindings in the short bar. Set it if the
+// detail pane doesn't show them.
+func (m *Model) SetActions(on bool) { m.actions = on }
+
 func (m *Model) SetWidth(w int) {
 	m.width = w
 	m.help.Width = w - 2
@@ -62,5 +73,29 @@ func (m Model) View() string {
 	if m.flash != "" {
 		return style.Foreground(m.theme.Warn).Render(m.flash)
 	}
+	if m.help.ShowAll {
 		return style.Render(m.help.View(m.keys))
+	}
+	return style.Render(m.shortBar(m.width - 2))
+}
+
+// shortBar puts the global keys on the right and as many of the others on the
+// left as fit; the submodule keys are dropped first.
+func (m Model) shortBar(w int) string {
+	h := m.help
+	h.Width = 0
+	right := h.ShortHelpView(m.keys.Global())
+	left := m.keys.Navigation()
+	if m.actions {
+		left = append(left[:len(left):len(left)], m.keys.Submodule()...)
+	}
+	for ; ; left = left[:len(left)-1] {
+		l := h.ShortHelpView(left)
+		if gap := w - lipgloss.Width(l) - lipgloss.Width(right); gap >= 2 || len(left) == 0 {
+			if gap < 0 { // not even the global keys fit
+				return ansi.Truncate(right, w, "…")
+			}
+			return l + strings.Repeat(" ", gap) + right
+		}
+	}
 }

internal/tui/keys.go

@@ -7,7 +7,7 @@ type keyMap struct {
 	CollapseAll, ExpandAll                      key.Binding
 	Home, End, PageUp, PageDown                 key.Binding
 	Update, Bump, Fetch, Reload, Filter, Issues key.Binding
-	Help, Quit                                  key.Binding
+	Copy, Help, Quit                            key.Binding
 }
 
 func defaultKeys() keyMap {
@@ -29,16 +29,29 @@ func defaultKeys() keyMap {
 		Reload:      key.NewBinding(key.WithKeys("r"), key.WithHelp("r", "reload")),
 		Filter:      key.NewBinding(key.WithKeys("/"), key.WithHelp("/", "filter")),
 		Issues:      key.NewBinding(key.WithKeys("!"), key.WithHelp("!", "problems only")),
+		Copy:        key.NewBinding(key.WithKeys("c"), key.WithHelp("c", "copy path")),
 		Help:        key.NewBinding(key.WithKeys("?"), key.WithHelp("?", "help")),
 		Quit:        key.NewBinding(key.WithKeys("q", "ctrl+c"), key.WithHelp("q", "quit")),
 	}
 }
 
-func (k keyMap) ShortHelp() []key.Binding {
+// Navigation returns the bindings that move the selection or fold the tree.
+func (k keyMap) Navigation() []key.Binding {
 	move := key.NewBinding(key.WithKeys("up"), key.WithHelp("↑↓/jk", "move"))
 	fold := key.NewBinding(key.WithKeys("left"), key.WithHelp("←→/hl", "fold"))
 	all := key.NewBinding(key.WithKeys("H"), key.WithHelp("⇧←→/HL", "fold all"))
-	return []key.Binding{move, fold, all, k.Toggle, k.Help, k.Quit}
+	return []key.Binding{move, fold, all, k.Toggle}
+}
+
+// Submodule returns the bindings that act on the selected submodule. They
+// are shown in the detail pane, or in the footer if the pane can't show them.
+func (k keyMap) Submodule() []key.Binding { return []key.Binding{k.Copy} }
+
+// Global returns the bindings that don't depend on the selection.
+func (k keyMap) Global() []key.Binding { return []key.Binding{k.Help, k.Quit} }
+
+func (k keyMap) ShortHelp() []key.Binding {
+	return append(append(k.Navigation(), k.Submodule()...), k.Global()...)
 }
 
 func (k keyMap) FullHelp() [][]key.Binding {
@@ -46,7 +59,8 @@ func (k keyMap) FullHelp() [][]key.Binding {
 		{k.Up, k.Down, k.Left, k.Right, k.Toggle},
 		{k.CollapseAll, k.ExpandAll},
 		{k.Home, k.End, k.PageUp, k.PageDown},
-		{k.Update, k.Bump, k.Fetch, k.Reload, k.Filter, k.Issues},
+		{k.Copy, k.Update, k.Bump},
+		{k.Fetch, k.Reload, k.Filter, k.Issues},
 		{k.Help, k.Quit},
 	}
 }

internal/tui/theme/help.go

@@ -0,0 +1,15 @@
+package theme
+
+import "github.com/charmbracelet/bubbles/help"
+
+// NewHelp returns a help renderer in the theme's colors.
+func NewHelp(t Theme) help.Model {
+	h := help.New()
+	h.Styles.ShortKey = Fg(t.Text).Bold(true)
+	h.Styles.ShortDesc = Fg(t.Muted)
+	h.Styles.ShortSeparator = Fg(t.Border)
+	h.Styles.FullKey = h.Styles.ShortKey
+	h.Styles.FullDesc = h.Styles.ShortDesc
+	h.Styles.FullSeparator = h.Styles.ShortSeparator
+	return h
+}

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.firstNode()
-		m.cursor = m.rows()[m.firstNodeRow()].node
-	}
 }
 
 // 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 {
+	if m.cursor == nil {
-		m.cursor = m.rows()[m.firstNodeRow()].node
+		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 := "  "

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
+}

scripts/make-fixture.sh

@@ -72,6 +72,8 @@ g "$w" push origin main
 g "$root/work/log" submodule add "$root/remotes/nested.git" modules/nested
 g "$root/work/log" commit -m "Add nested"
 g "$root/work/log" push origin main
+# "archive" ties with main (same tip, sorts first) -> the preferred ref wins
+g "$root/work/log" push origin main:archive
 
 super="$root/super"
 git init -q "$super"
@@ -88,6 +90,7 @@ add ui libs/staged
 add net libs/missing
 add ui vendor
 add work libs/work
+add feature libs/topic -b main
 g "$super" submodule update --init --recursive
 g "$super" commit -m "Add submodules"
 
@@ -109,6 +112,13 @@ g "$super/libs/feature" checkout origin/feat/search~1
 g "$super" add libs/feature
 g "$super" commit -m "Pin feature search"
 
+# libs/topic: .gitmodules says main, but the pin is the tip of feat/search
+# -> the closest branch wins over the configured one
+g "$super/libs/topic" fetch
+g "$super/libs/topic" checkout origin/feat/search
+g "$super" add libs/topic
+g "$super" commit -m "Pin topic search"
+
 # src/core: checkout moved away from the pin -> off pin
 g "$super/src/core" checkout HEAD~1