refactor: delegate -l output to findmnt

The custom one-alias-per-line output was useless — no mountpoint, no
source, no options. Reinventing a table format when findmnt from
util-linux already produces a familiar fuse.sshfs view was the wrong
call. -l now shells out to findmnt -t fuse.sshfs.

DECISIONS.md

@@ -1,5 +1,35 @@
 # Decisions
 
+## 2026-05-04 – Delegate `-l` output to `findmnt -t fuse.sshfs`
+- **Who**: Dom, ClaudeCode
+- **Why**: The custom `-l` output ("just the alias, one per line") was
+  uselessly minimal — no mountpoint, no source, no options. Reinventing a
+  table format for a single command was the wrong call when `findmnt` from
+  `util-linux` already produces a familiar, well-formatted view of fuse.sshfs
+  mounts.
+- **Tradeoffs**:
+  - External dependency on `findmnt` (part of `util-linux`, present on every
+    Arch and most other Linux systems by default — no real adoption cost).
+  - Output is mountpoint-first, not alias-first. The alias is only visible as
+    the last path segment under the SOURCE column / TARGET basename.
+  - Lists *all* fuse.sshfs mounts on the system, not just sshfsc-managed
+    ones under `$XDG_RUNTIME_DIR/sshfs/`. In practice this is what the user
+    wants ("show me all sshfs mounts"); a future `-r` (restrict) flag could
+    narrow it if needed.
+  - `findmnt` exits 1 when nothing matches its filter — we treat that as
+    success-with-empty-output, not a failure.
+- **How**:
+  - `list_mounts` rewritten as a thin wrapper around `exec.Command("findmnt",
+    "-t", "fuse.sshfs")` with stdout piped to the caller's writer.
+  - Exit-code 1 from `findmnt` is swallowed via `errors.As(err, *exec.ExitError)`
+    + `ExitCode() == 1`.
+  - `errors.Is(err, exec.ErrNotFound)` produces a clear "install util-linux"
+    message instead of a cryptic exec error.
+  - Tests `TestListMountsMissingBase` and `TestListMountsFiltersUnmounted`
+    removed: they covered the old in-Go enumeration logic that no longer
+    exists. Mocking `findmnt` would be alibi-testing — the wrapper is two
+    branches over `cmd.Run()`'s error.
+
 ## 2026-05-04 – Detect mounts via `/proc/self/mountinfo` instead of `stat`
 - **Who**: Dom, ClaudeCode
 - **Why**: `mountinfo.Mounted(path)` from `github.com/moby/sys/mountinfo` works

README.md

@@ -22,6 +22,7 @@ install -Dm755 sshfsc /usr/local/bin/sshfsc
 # Dependencies
 
 - [SSHFS](https://wiki.archlinux.org/title/SSHFS)
+- `findmnt` from `util-linux` (for `-l`)
 - [Go](https://wiki.archlinux.org/title/Go) >= 1.25 (build-time)
 
 # Usage
@@ -39,7 +40,7 @@ sshfsc -l              # list active mounts
 | `-e` | open mountpoint in your editor |
 | `-v` | verbose: print resolved ssh_config fields (HostName, User, Port, IdentityFile) |
 | `-r`, `--remote-dir <path>` | remote directory to mount (default: remote home) |
-| `-l` | list active mounts under `$XDG_RUNTIME_DIR/sshfs/` and exit |
+| `-l` | list active fuse.sshfs mounts via `findmnt` and exit |
 | `-u` | unmount the given `<Host>` and exit (mutually exclusive with `-l`) |
 
 By default only the resolved mount path is printed. Use `-v` for the full

main.go

@@ -281,26 +281,22 @@ func is_mounted_at(path string) (bool, error) {
 }
 
 func list_mounts(out io.Writer) error {
-	base, err := mount_base(false)
-	if err != nil {
-		if errors.Is(err, fs.ErrNotExist) {
+	cmd := exec.Command("findmnt", "-t", "fuse.sshfs")
+	cmd.Stdout = out
+	cmd.Stderr = os.Stderr
+	err := cmd.Run()
+	if err == nil {
 		return nil
 	}
-		return err
-	}
-	mounts, err := mountinfo.GetMounts(mountinfo.PrefixFilter(base))
-	if err != nil {
-		return fmt.Errorf("read mountinfo: %w", err)
-	}
-	prefix := base + string(os.PathSeparator)
-	for _, m := range mounts {
-		rel := strings.TrimPrefix(m.Mountpoint, prefix)
-		if rel == "" || strings.Contains(rel, string(os.PathSeparator)) {
-			continue
-		}
-		fmt.Fprintln(out, rel)
-	}
+	// findmnt exits 1 when no matching mount exists — not an error here.
+	var ee *exec.ExitError
+	if errors.As(err, &ee) && ee.ExitCode() == 1 {
 		return nil
+	}
+	if errors.Is(err, exec.ErrNotFound) {
+		return fmt.Errorf("findmnt not found (install util-linux)")
+	}
+	return fmt.Errorf("findmnt: %w", err)
 }
 
 func run_fusermount(flag, mount string) error {

main_test.go

@@ -4,7 +4,6 @@
 package main
 
 import (
-	"bytes"
 	"os"
 	"path/filepath"
 	"strings"
@@ -140,36 +139,6 @@ func TestVerifyMountDirRejectsSymlink(t *testing.T) {
 	}
 }
 
-func TestListMountsMissingBase(t *testing.T) {
-	runtime := t.TempDir()
-	t.Setenv("XDG_RUNTIME_DIR", runtime)
-	var buf bytes.Buffer
-	if err := list_mounts(&buf); err != nil {
-		t.Fatalf("unexpected error: %v", err)
-	}
-	if buf.Len() != 0 {
-		t.Fatalf("want empty output, got %q", buf.String())
-	}
-}
-
-func TestListMountsFiltersUnmounted(t *testing.T) {
-	runtime := t.TempDir()
-	t.Setenv("XDG_RUNTIME_DIR", runtime)
-	base := filepath.Join(runtime, "sshfs")
-	for _, name := range []string{"stale1", "stale2"} {
-		if err := os.MkdirAll(filepath.Join(base, name), 0700); err != nil {
-			t.Fatalf("setup stale dir: %v", err)
-		}
-	}
-	var buf bytes.Buffer
-	if err := list_mounts(&buf); err != nil {
-		t.Fatalf("unexpected error: %v", err)
-	}
-	if buf.Len() != 0 {
-		t.Fatalf("want stale dirs filtered, got %q", buf.String())
-	}
-}
-
 func TestUnmountRejectsBadAlias(t *testing.T) {
 	runtime := t.TempDir()
 	t.Setenv("XDG_RUNTIME_DIR", runtime)