feat: add --remote-dir flag and use ssh alias as mount label

- New `-r` / `--remote-dir` flag to mount a specific remote subdirectory;
  empty default preserves prior home-dir behaviour.
- Validate the flag value via a dedicated `rxRemoteDir` allowlist before it
  reaches the sshfs argv.
- Use the ssh_config alias (not the resolved HostName) as the local
  mountpoint name and as the sshfs source. File managers now show the
  human-readable label instead of the raw IP.
- Validate `args[0]` against `rxHostUser` since it now flows into argv.
- Rename `verify_mount_dir` parameter `hostname -> name` and `mount_sshfs`
  first parameter `hostname -> alias` for clarity.

DECISIONS.md

@@ -1,6 +1,51 @@
 # Decisions
 
-## 2026-04-26 – Audit remediation: cache flag, host-key policy, argv hardening
+## 2026-04-28 – Use ssh_config alias as label for mountpoint and sshfs source
+- **Who**: Dom, ClaudeCode
+- **Why**: File managers showed the resolved `HostName` (often a raw IP) for
+  both the mount source (`user@10.0.0.5:`) and the mountpoint directory
+  (`~/Servers/10.0.0.5/`). The ssh_config alias is the human-readable label;
+  using it makes mounts identifiable in Nautilus/Dolphin/etc.
+- **Tradeoffs**:
+  - sshfs now resolves the alias internally via `~/.ssh/config` instead of
+    receiving a pre-resolved IP. Our explicit `-o IdentityFile=` and `-p port`
+    still win as overrides — the resolved values were redundant but kept as a
+    belt-and-suspenders sanity check (early failure if config is malformed).
+  - The CLI argument flows into the sshfs argv, so it must be validated.
+    Added `validate_ssh_field("alias", args[0], rxHostUser)` immediately after
+    arg parsing to gate injection-shaped input.
+  - Existing mounts under `~/Servers/<ip>/` are now orphaned. User must
+    manually `fusermount -u` and `rmdir` the IP-named directories. Documented
+    in the README pointer.
+- **How**:
+  - `args[0]` captured into `alias`, validated via `rxHostUser`.
+  - `verify_mount_dir(alias)` instead of `(hostname)`; param renamed to `name`
+    for clarity since it no longer represents a resolved hostname.
+  - `mount_sshfs` first arg renamed `hostname → alias`; argv source string
+    becomes `user+"@"+alias+":"+remoteDir`.
+
+## 2026-04-28 – Add `-r` / `--remote-dir` flag for custom remote path
+- **Who**: Dom, ClaudeCode
+- **Why**: Mounting only the remote home was too restrictive; sometimes a
+  specific subdirectory (e.g. `/var/www`, `~/projects`) is the actual target.
+- **Tradeoffs**:
+  - Two flag aliases (`-r` and `--remote-dir`) registered against the same
+    target via `flag.StringVar`. Doubles the `flag.PrintDefaults` output but
+    matches typical short/long convention.
+  - `rxRemoteDir` deliberately stricter than `rxIdentityFile` — no `:`, `@`,
+    `+`, `=`, `%` since remote paths rarely need them and looser allowlists
+    invite injection-shaped surprises in the `user@host:path` argv slot.
+  - Local mount path stays `~/Servers/<host>` regardless of remote dir — one
+    host = one mountpoint, even if `-r` differs between invocations. Re-mount
+    requires `fusermount -u` first.
+- **How**:
+  - `rDir` package-level `string`, registered in `init()` as `r` and
+    `remote-dir`; validated against `rxRemoteDir = ^[A-Za-z0-9/~][A-Za-z0-9._/~-]*$`.
+  - `mount_sshfs` signature gains `remoteDir string`; appended to the
+    `user@host:` argv slot. Empty string preserves the previous home-dir
+    default.
+  - `-v` output includes `Remote:` line when `rDir` is set.
+  - Tests extended with eight `rxRemoteDir` boundary cases.
 - **Who**: Dom, ClaudeCode
 - **Why**: Audit found `kernel_cache` causes stale reads on a network FS;
   `StrictHostKeyChecking` was implicit (depended on system default);

README.md

@@ -1,6 +1,6 @@
 Quickly mount remote systems via SSHFS based on your ssh_config
 
-Static mount dir is currently `~/Servers/<Host>`
+Static mount dir is currently `~/Servers/<Host>` (uses the ssh_config alias as label, not the resolved IP).
 
 # Install
 
@@ -36,6 +36,7 @@ sshfsc <Host>
 | ---- | ----------- |
 | `-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) |
 
 By default only the resolved mount path is printed. Use `-v` for the full
 ssh_config dump.

main.go

@@ -20,13 +20,20 @@ import (
 var (
 	rxHostUser     = regexp.MustCompile(`^[A-Za-z0-9_][A-Za-z0-9._-]*$`)
 	rxIdentityFile = regexp.MustCompile(`^[A-Za-z0-9/~][A-Za-z0-9._@/:+=~%-]*$`)
+	rxRemoteDir    = regexp.MustCompile(`^[A-Za-z0-9/~][A-Za-z0-9._/~-]*$`)
 )
 
 var (
 	eFlag = flag.Bool("e", false, "open mountpoint in your editor")
 	vFlag = flag.Bool("v", false, "verbose: print resolved ssh_config fields")
+	rDir  string
 )
 
+func init() {
+	flag.StringVar(&rDir, "r", "", "remote directory to mount (default: remote home)")
+	flag.StringVar(&rDir, "remote-dir", "", "remote directory to mount (default: remote home)")
+}
+
 func main() {
 	flag.Usage = func() {
 		fmt.Fprintf(os.Stderr,
@@ -43,6 +50,12 @@ func main() {
 		os.Exit(2)
 	}
 
+	alias := args[0]
+	if err := validate_ssh_field("alias", alias, rxHostUser); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(3)
+	}
+
 	hostname, err := lookup_ssh_field(args[0], "HostName")
 	if err != nil {
 		fmt.Fprintln(os.Stderr, err)
@@ -96,8 +109,14 @@ func main() {
 		fmt.Fprintf(os.Stderr, "ssh config Port %q is not a valid port number\n", port)
 		os.Exit(3)
 	}
+	if rDir != "" {
+		if err := validate_ssh_field("remote-dir", rDir, rxRemoteDir); err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			os.Exit(3)
+		}
+	}
 
-	mount, err := verify_mount_dir(hostname)
+	mount, err := verify_mount_dir(alias)
 	if err != nil {
 		fmt.Fprintln(os.Stderr, "verify_mount_dir() failed:", err)
 		os.Exit(4)
@@ -109,6 +128,9 @@ func main() {
 		fmt.Println("Port:		", port)
 		fmt.Println("Ifile:		", ifile)
 		fmt.Println("Mount:		", mount)
+		if rDir != "" {
+			fmt.Println("Remote:		", rDir)
+		}
 		fmt.Println("---")
 	} else {
 		fmt.Println("Mount:	", mount)
@@ -120,7 +142,7 @@ func main() {
 		os.Exit(5)
 	}
 	if !chkmount {
-		if err := mount_sshfs(hostname, user, ifile, port, mount); err != nil {
+		if err := mount_sshfs(alias, user, ifile, port, mount, rDir); err != nil {
 			fmt.Fprintln(os.Stderr, "mount_sshfs() failed:", err)
 			os.Exit(6)
 		}
@@ -160,7 +182,7 @@ func run_editor(mount string) error {
 	return cmd.Start()
 }
 
-func verify_mount_dir(hostname string) (string, error) {
+func verify_mount_dir(name string) (string, error) {
 	homedir, err := os.UserHomeDir()
 	if err != nil {
 		return "", fmt.Errorf("resolve home dir: %w", err)
@@ -173,9 +195,9 @@ func verify_mount_dir(hostname string) (string, error) {
 	if err != nil {
 		return "", fmt.Errorf("resolve base %q: %w", base, err)
 	}
-	mount := filepath.Clean(filepath.Join(realBase, hostname))
+	mount := filepath.Clean(filepath.Join(realBase, name))
 	if !strings.HasPrefix(mount, realBase+string(os.PathSeparator)) {
-		return "", fmt.Errorf("hostname %q escapes mount base %q", hostname, realBase)
+		return "", fmt.Errorf("name %q escapes mount base %q", name, realBase)
 	}
 	if info, err := os.Lstat(mount); err == nil && info.Mode()&os.ModeSymlink != 0 {
 		return "", fmt.Errorf("mount path %q is a symlink", mount)
@@ -186,7 +208,7 @@ func verify_mount_dir(hostname string) (string, error) {
 	return mount, nil
 }
 
-func mount_sshfs(hostname string, user string, ifile string, port string, mount string) error {
+func mount_sshfs(alias string, user string, ifile string, port string, mount string, remoteDir string) error {
 	cmd := exec.Command("sshfs", "-p", port,
 		"-o", "IdentityFile="+ifile,
 		"-o", "idmap=user",
@@ -201,7 +223,7 @@ func mount_sshfs(hostname string, user string, ifile string, port string, mount
 		"-o", "StrictHostKeyChecking=accept-new",
 		"-o", "ServerAliveInterval=15",
 		"-o", "ServerAliveCountMax=3",
-		user+"@"+hostname+":", mount)
+		user+"@"+alias+":"+remoteDir, mount)
 	cmd.Stdout = os.Stdout
 	cmd.Stderr = os.Stderr
 	return cmd.Run()

main_test.go

@@ -92,12 +92,24 @@ func TestValidateSSHFieldRegexes(t *testing.T) {
 		{"identityfile leading dot rejected", ".ssh/id", "ifile", false},
 		{"identityfile leading colon rejected", ":weird", "ifile", false},
 		{"identityfile empty rejected", "", "ifile", false},
+
+		{"remote-dir absolute", "/var/www", "rdir", true},
+		{"remote-dir tilde", "~/work", "rdir", true},
+		{"remote-dir relative", "projects/foo", "rdir", true},
+		{"remote-dir leading dash rejected", "-rf", "rdir", false},
+		{"remote-dir leading dot rejected", "./x", "rdir", false},
+		{"remote-dir space rejected", "/var /www", "rdir", false},
+		{"remote-dir comma rejected", "/a,b", "rdir", false},
+		{"remote-dir empty rejected", "", "rdir", false},
 	}
 	for _, tc := range cases {
 		t.Run(tc.name, func(t *testing.T) {
 			var rx = rxHostUser
-			if tc.rx == "ifile" {
+			switch tc.rx {
+			case "ifile":
 				rx = rxIdentityFile
+			case "rdir":
+				rx = rxRemoteDir
 			}
 			err := validate_ssh_field("X", tc.value, rx)
 			if tc.ok && err != nil {