pacman: user --groups instead of --group (#4312)

* s/group/groups/

Pacman accepts --group but the actual option name is --groups.
Allows use of other binaries with the same CLI interface as pacman (yay)

* changelog

* Apply suggestions from code review

Co-authored-by: Felix Fontein <felix@fontein.de>

* Add note regarding pacman compat + --print-format

* Update plugins/modules/packaging/os/pacman.py

Co-authored-by: Felix Fontein <felix@fontein.de>

Co-authored-by: Felix Fontein <felix@fontein.de>

changelogs/fragments/4312-pacman-groups.yml

@@ -0,0 +1,9 @@
+bugfixes:
+  - pacman - Use ``--groups`` instead of ``--group``
+    (https://github.com/ansible-collections/community.general/pull/4312).
+
+known_issues:
+   - pacman - binaries specified in the ``executable`` parameter must support
+     ``--print-format`` in order to be used by this module.
+     In particular, AUR helper ``yay`` is known not to currently support it
+     (https://github.com/ansible-collections/community.general/pull/4312).

plugins/modules/packaging/os/pacman.py

@@ -52,7 +52,10 @@ options:
 
     executable:
         description:
-            - Name of binary to use. This can either be C(pacman) or a pacman compatible AUR helper.
+            - Path of the binary to use. This can either be C(pacman) or a pacman compatible AUR helper.
+            - Pacman compatibility is unfortunately ill defined, in particular, this modules makes
+              extensive use of the C(--print-format) directive which is known not to be implemented by
+              some AUR helpers (notably, C(yay)).
             - Beware that AUR helpers might behave unexpectedly and are therefore not recommended.
         default: pacman
         type: str
@@ -575,7 +578,7 @@ class Pacman(object):
 
         installed_groups = defaultdict(set)
         dummy, stdout, dummy = self.m.run_command(
-            [self.pacman_path, "--query", "--group"], check_rc=True
+            [self.pacman_path, "--query", "--groups"], check_rc=True
         )
         # Format of lines:
         #     base-devel file
@@ -600,7 +603,7 @@ class Pacman(object):
 
         available_groups = defaultdict(set)
         dummy, stdout, dummy = self.m.run_command(
-            [self.pacman_path, "--sync", "--group", "--group"], check_rc=True
+            [self.pacman_path, "--sync", "--groups", "--groups"], check_rc=True
         )
         # Format of lines:
         #     vim-plugins vim-airline