feat: add -l (list) and -u (unmount) flags

A second sshfsc <alias> call only printed "Already mounted"; tearing
down a mount required ls + fusermount by hand. -l lists active mounts
verified via mountinfo.Mounted, -u <Host> unmounts and removes the
empty mountpoint dir. Flags are mutually exclusive.

README.md

@@ -27,7 +27,9 @@ install -Dm755 sshfsc /usr/local/bin/sshfsc
 # Usage
 
 ```
-sshfsc <Host>
+sshfsc <Host>          # mount
+sshfsc -u <Host>       # unmount
+sshfsc -l              # list active mounts
 ```
 
 ## Arguments
@@ -37,6 +39,8 @@ 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) |
+| `-l` | list active mounts under `$XDG_RUNTIME_DIR/sshfs/` 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
 ssh_config dump.