4 files changed, 101 insertions, 11 deletions

diff --git a/guix/channels.scm b/guix/channels.scm
index 662fc7bae22..ac9303c5fa0 100644
--- a/guix/channels.scm
+++ b/guix/channels.scm
@@ -5,6 +5,7 @@
 ;;; Copyright © 2021 Brice Waegeneire <brice@waegenei.re>
 ;;; Copyright © 2024 Julien Lepiller <julien@lepiller.eu>
 ;;; Copyright © 2024 Rostislav Svoboda <Rostislav.Svoboda@gmail.com>
+;;; Copyright © 2026 Simon Tournier <zimon.toutoune@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -245,13 +246,18 @@ could be found at DIRECTORY or one of its ancestors."
 (define (channel-reference channel)
   "Return the \"reference\" for CHANNEL, an sexp suitable for
 'latest-repository-commit'."
-  (match (channel-commit channel)
-    (#f      (let ((branch (channel-branch channel)))
-               (if (and (string? branch)
-                        (string-prefix? "refs/" branch))
-                   `(symref . ,branch)
-                   `(branch . ,branch))))
-    (commit  `(tag-or-commit . ,(channel-commit channel)))))
+  (let* ((commit (channel-commit channel))
+         (branch (channel-branch channel))
+         (refs? (and branch
+                     (string? branch)
+                     (string-prefix? "refs/" branch))))
+    (if commit
+        (if refs?
+            `(symref        . (,branch . ,commit))
+            `(tag-or-commit . ,commit))
+        (if refs?
+            `(symref . ,branch)
+            `(branch . ,branch)))))
 
 (define sexp->channel-introduction
   (match-lambda
diff --git a/guix/git.scm b/guix/git.scm
index f6fab9fc914..4107acd4867 100644
--- a/guix/git.scm
+++ b/guix/git.scm
@@ -5,7 +5,7 @@
 ;;; Copyright © 2021 Marius Bakke <marius@gnu.org>
 ;;; Copyright © 2022 Maxime Devos <maximedevos@telenet.be>
 ;;; Copyright © 2023 Tobias Geerinckx-Rice <me@tobias.gr>
-;;; Copyright © 2023, 2025 Simon Tournier <zimon.toutoune@gmail.com>
+;;; Copyright © 2023, 2025, 2026 Simon Tournier <zimon.toutoune@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -273,9 +273,14 @@ corresponding Git object."
        (let ((oid (reference-target
                    (branch-lookup repository branch BRANCH-REMOTE))))
          (object-lookup repository oid)))
-      (('symref . symref)
+      (('symref . (? string? symref))
        (let ((oid (reference-name->oid repository symref)))
-         (object-lookup repository oid)))
+            (object-lookup repository oid)))
+      (('symref . (_ . commit))
+       ;; It handles channel files automatically generated by Cuirass, where
+       ;; the branch follows Pull-Request Git namespace as refs/pull/1/head,
+       ;; and one commit is specifically pinned on that symref branch.
+       (resolve `(commit . ,commit)))
       (('commit . commit)
        (let ((len (string-length commit)))
          ;; 'object-lookup-prefix' appeared in Guile-Git in Mar. 2018, so we
@@ -437,6 +442,8 @@ definitely available in REPOSITORY, false otherwise."
          ('tag-or-commit . str))
      (false-if-git-not-found
       (->bool (resolve-reference repository ref))))
+    (('symref . (_ . (? commit-id? commit)))
+     (reference-available? repository `(commit . ,commit)))
     (_
      ;; For the others REF as branch or symref, the REF cannot be available
      #f)))
@@ -588,7 +595,8 @@ current settings unchanged."
 
   (define ref->refspecs
     (match-lambda
-      (('symref . symref)
+      ((or ('symref . (? string? symref))
+           ('symref . (symref . _)))
        (list (string-append "+" symref ":" symref)))
        (_ '())))
 
diff --git a/guix/tests/git.scm b/guix/tests/git.scm
index a649c1fa6e8..35a41470eb1 100644
--- a/guix/tests/git.scm
+++ b/guix/tests/git.scm
@@ -1,6 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2019, 2020, 2021 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2021 Xinglu Chen <public@yoctocell.xyz>
+;;; Copyright © 2026 Simon Tournier <zimon.toutoune@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -120,6 +121,9 @@ Return DIRECTORY on success."
        (loop rest))
       ((('reset to) rest ...)
        (git "reset" "--hard" to)
+       (loop rest))
+      ((('symbolic-ref name ref) rest ...)
+       (git "symbolic-ref" name ref)
        (loop rest)))))
 
 (define (call-with-temporary-git-repository directives proc)
diff --git a/tests/git.scm b/tests/git.scm
index 9ccd04f0cdf..712b12c7fc4 100644
--- a/tests/git.scm
+++ b/tests/git.scm
@@ -1,6 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2019-2020, 2022, 2024 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2021 Xinglu Chen <public@yoctocell.xyz
+;;; Copyright © 2026 Simon Tournier <zimon.toutoune@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -279,4 +280,75 @@
            (not (file-exists?
                  (in-vicinity cache "stale-untracked-file")))))))))
 
+(test-assert "update-cached-checkout, symref tag"
+  (call-with-temporary-directory
+   (lambda (cache)
+     (with-temporary-git-repository directory
+         '((add "a.txt" "A")
+           (commit "First commit")
+           (tag "v1.0" "release-1.0")
+           (branch "develop")
+           (checkout "develop")
+           (add "b.txt" "B")
+           (commit "Second commit")
+           (tag "v1.1" "release-1.1")
+           (checkout "master"))
+       (let* ((tag-directory   (let* ((pipe (open-pipe* OPEN_READ (git-command)
+                                                        "-C" directory
+                                                        "rev-parse" "v1.1"))
+                                      (str  (get-string-all pipe)))
+                                 (close-pipe pipe)
+                                 (string-trim-right str)))
+              (cached-directory commit relation
+                                (update-cached-checkout directory
+                                                        #:ref '(symref . "refs/tags/v1.1")
+                                                        #:cache-directory cache))
+              (head-cached   (let* ((pipe (open-pipe* OPEN_READ (git-command)
+                                                      "-C" cached-directory
+                                                      ;; switch-to-ref doesn't dereference the Git object,
+                                                      ;; thus it points to a Git tag object.
+                                                      ;; And HEAD points to a Git commit object.
+                                                      ;; Hence, the check is against Git tag objects.
+                                                      ;; For the difference see:
+                                                      ;;   git show-ref --dereference v1.1
+                                                      "rev-parse" "v1.1"))
+                                    (str  (get-string-all pipe)))
+                               (close-pipe pipe)
+                               (string-trim-right str))))
+         (and (string=? commit        head-cached)
+              (string=? tag-directory head-cached)))))))
+
+(test-assert "update-cached-checkout, symref pull-request"
+  (call-with-temporary-directory
+   (lambda (cache)
+     (with-temporary-git-repository directory
+         '((add "a.txt" "A")
+           (commit "First commit")
+           (tag "v1.0" "release-1.0")
+           (branch "develop")
+           (checkout "develop")
+           (add "b.txt" "B")
+           (commit "Second commit")
+           (tag "v1.1" "release-1.1")
+           (symbolic-ref "refs/pull/1/head" "refs/heads/develop")
+           (checkout "master"))
+       (let* ((head-directory   (let* ((pipe (open-pipe* OPEN_READ (git-command)
+                                                         "-C" directory
+                                                         "rev-parse" "refs/pull/1/head"))
+                                       (str  (get-string-all pipe)))
+                                  (close-pipe pipe)
+                                  (string-trim-right str)))
+              (cached-directory commit relation
+                                (update-cached-checkout directory
+                                                        #:ref '(symref . "refs/pull/1/head")
+                                                        #:cache-directory cache))
+              (head-cached   (let* ((pipe (open-pipe* OPEN_READ (git-command)
+                                                      "-C" cached-directory
+                                                      "rev-parse" "HEAD"))
+                                    (str  (get-string-all pipe)))
+                               (close-pipe pipe)
+                               (string-trim-right str))))
+         (and (string=? commit      head-directory)
+              (string=? head-cached head-directory)))))))
+
 (test-end "git")