[release-branch.go1.23] cmd/go/internal/modfetch: do not trust server to send all...

Newer git versions (at least git 2.47.1) do not send all the matching tags
for a shallow fetch of a specific hash anymore. The go command assumes
that git servers do this. Since that assumption is broken, use the local
copy of the remote refs list to augment the tags sent by the server.
This makes the cmd/go/internal/modfetch tests pass again with newer git.

For #71261
Fixes #71263

Change-Id: I9fd4f3fd7beeb68a522938599f8f3acd887d0b26
Reviewed-on: https://go-review.googlesource.com/c/go/+/642437
Reviewed-by: Michael Matloob <matloob@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Russ Cox <rsc@golang.org>
(cherry picked from commit bd80d8956f3062d2b2bff2d7da6b879dfa909f12)
Reviewed-on: https://go-review.googlesource.com/c/go/+/642696
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>

diff --git a/src/cmd/go/internal/modfetch/codehost/git.go b/src/cmd/go/internal/modfetch/codehost/git.go
index bab4c5ebbedba4a25c8215752b3606b757edf117..9996be7af7e4243db409fe041796e0e4c67a1b8a 100644 (file)
--- a/src/cmd/go/internal/modfetch/codehost/git.go
+++ b/src/cmd/go/internal/modfetch/codehost/git.go
@@ -662,7 +662,21 @@ func (r *gitRepo) statLocal(ctx context.Context, version, rev string) (*RevInfo,
                        }
                }
        }
-       sort.Strings(info.Tags)
+
+       // Git 2.47.1 does not send the tags during shallow clone anymore
+       // (perhaps the exact version that changed behavior is an earlier one),
+       // so we have to also add tags from the refs list we fetched with ls-remote.
+       if refs, err := r.loadRefs(ctx); err == nil {
+               for ref, h := range refs {
+                       if h == hash {
+                               if tag, found := strings.CutPrefix(ref, "refs/tags/"); found {
+                                       info.Tags = append(info.Tags, tag)
+                               }
+                       }
+               }
+       }
+       slices.Sort(info.Tags)
+       info.Tags = slices.Compact(info.Tags)
 
        // Used hash as info.Version above.
        // Use caller's suggested version if it appears in the tag list