[bug#48971] [PATCH 1/2] swh: Support lookup of Hg tags.

[Xinglu Chen <public@yoctocell.xyz>]

* guix/swh.scm (lookup-origin-revision): Support lookup of Hg tags, not just
Git tags.
---
I noticed that the ‘commit-id?’ procedure checks if REFERENCE is of
length 40, this will result in false negatives because some packages
that use ‘hg-fetch’ only specify the first ~10 or ~15 characters of the
changeset revision.  We should probably fix that.

 guix/swh.scm | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/guix/swh.scm b/guix/swh.scm
index f6d5241e06..b5c800011d 100644
--- a/guix/swh.scm
+++ b/guix/swh.scm
@@ -1,6 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2018, 2019, 2020, 2021 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2020 Jakub Kądziołka <kuba@kadziolka.net>
+;;; Copyright © 2021 Xinglu Chen <public@yoctocell.xyz>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -455,8 +456,13 @@ URL could not be found."
         ((visit . _)
          (let ((snapshot (visit-snapshot visit)))
            (match (and=> (find (lambda (branch)
-                                 (string=? (string-append "refs/tags/" tag)
-                                           (branch-name branch)))
+                                 (or
+                                  ;; Git specific.
+                                  (string=? (string-append "refs/tags/" tag)
+                                            (branch-name branch))
+                                  ;; Hg specific.
+                                  (string=? tag
+                                            (branch-name branch))))
                                (snapshot-branches snapshot))
                          branch-target)
              ((? release? release)
-- 
2.32.0