Add completion for pstree

[artemisart]

Description

Add completion for pstree https://www.man7.org/linux/man-pages/man1/pstree.1.html.

Is it possible to show a custom description for each argument value? Here I want to complete PIDs, it would be nice to show the process name in the tab options/search, but only complete with the PID.

pstree help for reference:

Usage: pstree [-acglpsStuZ] [ -h | -H PID ] [ -n | -N type ]
              [ -A | -G | -U ] [ PID | USER ]
       pstree -V
Display a tree of processes.

  -a, --arguments     show command line arguments
  -A, --ascii         use ASCII line drawing characters
  -c, --compact       don't compact identical subtrees
  -h, --highlight-all highlight current process and its ancestors
  -H PID,
  --highlight-pid=PID highlight this process and its ancestors
  -g, --show-pgids    show process group ids; implies -c
  -G, --vt100         use VT100 line drawing characters
  -l, --long          don't truncate long lines
  -n, --numeric-sort  sort output by PID
  -N type,
  --ns-sort=type      sort by namespace type (cgroup, ipc, mnt, net, pid,
                                              user, uts)
  -p, --show-pids     show PIDs; implies -c
  -s, --show-parents  show parents of the selected process
  -S, --ns-changes    show namespace transitions
  -t, --thread-names  show full thread names
  -T, --hide-threads  hide threads, show only processes
  -u, --uid-changes   show uid transitions
  -U, --unicode       use UTF-8 (Unicode) line drawing characters
  -V, --version       display version information
  -Z, --security-context
                      show SELinux security contexts
  PID    start at this PID; default is 1 (init)
  USER   show only trees rooted at processes of this user

TODOs:

• Changes to fish usage are reflected in user documentation/manpages.
• Tests have been added for regressions fixed
• User-visible changes noted in CHANGELOG.rst

[faho]

Is it possible to show a custom description for each argument value? Here I want to complete PIDs, it would be nice to show the process name in the tab options/search, but only complete with the PID.

See the completions for kill, which call a function that is made for this called __fish_complete_pids.

What you do is you print the completion candidate followed by a tab and its description, one candidate per line. But in this case you should be able to just call that function.

[artemisart]

Thanks @faho ! that's perfect

[faho]

Thanks, merged!