Make the terminal page support opening with a different path

[jelly]

Page: terminal

Cockpit-files has a feature request to open the terminal page in the current directory of files.

Currently the terminal page will default open the users home directory with a fallback to /. We want it to open a provided path for example via uri params, for example:

https://cockpit.org/system/terminal#/?path=/home

[martinpitt]

This shouldn't disrupt/stop the current terminal if it is currently running something. My first idea how to do "busy?" detection: cockpit-project/cockpit-files#464 (comment)

[martinpitt]

My recommendation: to unblock your work (for a few days), replace

spawn: [user.shell "/bin/bash"],

with something like

["/bin/sh", "-ec", "echo $$ > /tmp/terminal-pid; exec " + (user.shell || "/bin/bash")]

and use cockpit.file() to read the pid. This is an utter hack which we can't land, but I think there's enough unrelated work to be done here in the meantime. In the next days I'll see to teach the stream channel about exposing its pid.

[martinpitt]

@ashley-cui see #21132 for adding a proper API to get the pid.