teams: Add “codeowners” action.

* etc/teams.scm (team->codeowners-snippet, export-codeowners): New
procedures.
(main): Add “codeowners” action.
* doc/contributing.texi (Teams): Document it.

Change-Id: I601443981af374d85160833f7096d8c973873fb1

doc/contributing.texi

@@ -2733,6 +2733,13 @@ $ guix shell -D guix
 [env]$ git send-email --to=@var{ISSUE_NUMBER}@@debbugs.gnu.org -2
 @end example
 
+To generate a @file{CODEOWNERS} file, which Forgejo uses to determine
+which team or person should review changes to a given set of files, run:
+
+@example
+./etc/teams.scm codeowners > CODEOWNERS
+@end example
+
 @node Making Decisions
 @section Making Decisions
 

etc/teams.scm

@@ -14,6 +14,7 @@ exec $pre_inst_env_maybe guix repl -- "$0" "$@"
 ;;; Copyright © 2022 Simon Tournier <zimon.toutoune@gmail.com>
 ;;; Copyright © 2025 Jelle Licht <jlicht@fsfe.org>
 ;;; Copyright © 2025 Cayetano Santos <csantosb@inventati.org>
+;;; Copyright © 2025 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -1023,6 +1024,34 @@ and REV-END, two git revision strings."
        (find-team-by-scope (apply diff-revisions
                                   (git-patch->revisions patch-file)))))
 
+(define (team->codeowners-snippet team)
+  (string-join (map (lambda (scope)
+                      (format #f "~50a @guix/~a"
+                              (if (regexp*? scope)
+                                  (regexp*-pattern scope)
+                                  (regexp-quote scope))
+                              (team-id team)))
+                    (team-scope team))
+               "\n"
+               'suffix))
+
+(define (export-codeowners port)
+  (let ((teams (sort-teams
+                (hash-map->list (lambda (_ value) value) %teams))))
+    (display "\
+# This -*- conf -*- file was generated by './etc/teams.scm codeowners'.
+#
+# It describes the expected reviewers for a pull request based on the
+# changed files.  Unlike what the name of the file suggests they don't
+# own the code (ownership is collective in this house!) but merely have
+# a good understanding of that area of the codebase and therefore are
+# usually suited as a reviewer.\n\n"
+             port)
+    (for-each (lambda (team)
+                (display (team->codeowners-snippet team) port)
+                (newline port))
+              teams)))
+
 
 (define (main . args)
   (match args
@@ -1056,6 +1085,8 @@ and REV-END, two git revision strings."
       team-names))
     (("show" . team-names)
      (list-teams team-names))
+    (("codeowners")
+     (export-codeowners (current-output-port)))
     (anything
      (format (current-error-port)
              "Usage: etc/teams.scm <command> [<args>]