Add completions for OpenRC rc-service

This patch adds completions for the rc-service command from OpenRC, as
suggested and provided by Mathieu Roy via a Debian bug [1], fixed and
extended for more options by myself.

When ran on a chroot with a freshly bootstrapped Debian system, the
following completions produce the following output.

For the options:

  # rc-service [TAB][TAB]
  -c              -h              --ifstopped     -q              savecache
  -C              --help          kmod            --quiet         udev
  cron            -i              -l              -r              -v
  -d              -I              --list          rc              -V
  -D              --ifcrashed     -N              rcS             --verbose
  --debug         --ifexists      networking      --resolve       --version
  --dry-run       --ifinactive    --nocolor       rsyslog         -Z
  -e              --ifnotstarted  --nodeps        -s
  --exists        --ifstarted     procps          -S
  # rc-service [CURSOR]

  # rc-service -h[TAB]
  # rc-service -h [CURSOR]

  # rc-service --v[TAB]
  # rc-service --ver[CURSOR]

  # rc-service --ver[TAB][TAB]
  --verbose  --version
  # rc-service --ver[CURSOR]

  # rc-service --verbose --l[TAB]
  # rc-service --verbose --list [CURSOR]

For the services:

  # rc-service --list[ENTER]
  cron
  hwclock.sh
  kmod
  networking
  procps
  rc
  rcS
  rsyslog
  savecache
  udev

  # rc-service r[TAB][TAB]
  rc       rcS      rsyslog
  # rc-service r[CURSOR]

  # rc-service --dry-run cr[TAB]
  # rc-service --dry-run cron [CURSOR]

  # rc-service --dry-run cron [TAB][TAB]
  force-reload  reload        restart       start         status        stop
  # rc-service --dry-run cron [CURSOR]

  # rc-service --dry-run cron re[TAB][TAB]
  reload   restart
  # rc-service --dry-run cron re[CURSOR]

  # rc-service --dry-run cron res[TAB]
  # rc-service --dry-run cron restart [CURSOR]

Adding `set show-all-if-ambiguous on' to .inputrc yields the same
results, but without the need for the additional [TAB] as displayed
above.

[1] https://bugs.debian.org/865548

Gbp-Pq: Name 11-add-completions-for-openrc-rc-service.patch

completions/rc-service

@@ -0,0 +1,56 @@
+# rc-service(8) completion                                 -*- shell-script -*-
+#
+# Adapted from update-rc.d
+#
+# Copyright (C) 2004 Servilio Afre Puentes <servilio@gmail.com>
+#               2018 Mathieu Roy <yeupou@gnu.org>
+#               2018 Gabriel F. T. Gomes <gabriel@inconstante.eti.br>
+
+_rc_service()
+{
+    local cur prev words cword
+    _init_completion || return
+
+    local sysvdir services options valid_options
+
+    sysvdir=/etc/init.d
+
+    services=( $( printf '%s ' $sysvdir/!(README*|*.sh|$_backup_glob) ) )
+    services=( ${services[@]#$sysvdir/} )
+    options=( -d --debug \
+              -D --nodeps \
+              -e --exists \
+              -c --ifcrashed \
+              -i --ifexists \
+              -I --ifinactive \
+              -N --ifnotstarted \
+              -s --ifstarted \
+              -S --ifstopped \
+              -l --list \
+              -r --resolve \
+              -Z --dry-run \
+              -h --help \
+              -C --nocolor \
+              -V --version \
+              -v --verbose \
+              -q --quiet \
+    )
+
+
+    if [[ ($cword -eq 1) || ("$prev" == -* ) ]]; then
+        COMPREPLY=( $( compgen -W '${options[@]} ${services[@]}' \
+                               -- "$cur" ) )
+    elif [[ -x $sysvdir/$prev ]]; then
+        COMPREPLY=( $( compgen -W '`sed -e "y/|/ /" \
+                                        -ne "s/^.*Usage:[ ]*[^ ]*[ ]*{*\([^}\"]*\).*$/\1/p" \
+                                        $sysvdir/$prev`' \
+                               -- "$cur" ) )
+    else
+        COMPREPLY=()
+    fi
+
+    return 0
+} &&
+complete -F _rc_service rc-service
+
+# ex: filetype=sh