From ed3b3c794458372341cc5ac59a47d2d303760a2e Mon Sep 17 00:00:00 2001
From: Seongmin Lee <git@boltless.me>
Date: Thu, 14 May 2026 02:21:51 +0900
Subject: [PATCH] knotmirror/git: sync HEAD seperately on resync

Ideally this should be done by dedicated event like `gitHeadUpdate`, but
as we have lots of self-hosted knots, doing all the work from knotmirror
would be easier than requesting users to update their knot again.

Signed-off-by: Seongmin Lee <git@boltless.me>
---
 knotmirror/git.go | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/knotmirror/git.go b/knotmirror/git.go
index e87ae956..79d3776e 100644
--- a/knotmirror/git.go
+++ b/knotmirror/git.go
@@ -91,6 +91,38 @@ func (c *CliGitMirrorManager) fetch(ctx context.Context, path, url string) error
 		}
 		return fmt.Errorf("running 'git fetch': %w\n%s", err, string(out))
 	}
+
+	// TODO(boltless): make this dedicated event instead
+	lsRemoteCmd := exec.CommandContext(ctx, "git", "ls-remote", "--symref", url, "HEAD")
+	out, err := lsRemoteCmd.CombinedOutput()
+	if err != nil {
+		if ctx.Err() != nil {
+			return ctx.Err()
+		}
+		return fmt.Errorf("running 'git ls-remote --symref': %w\n%s", err, string(out))
+	}
+
+	var headRef string
+	for line := range strings.SplitSeq(string(out), "\n") {
+		if !strings.HasPrefix(line, "ref: ") {
+			continue
+		}
+		fields := strings.Fields(line)
+		if len(fields) >= 2 {
+			headRef = fields[1]
+			break
+		}
+	}
+	if headRef != "" {
+		symrefCmd := exec.CommandContext(ctx, "git", "-C", path, "symbolic-ref", "HEAD", headRef)
+		if out, err := symrefCmd.CombinedOutput(); err != nil {
+			if ctx.Err() != nil {
+				return ctx.Err()
+			}
+			return fmt.Errorf("running 'git symbolic-ref HEAD %s': %w\n%s", headRef, err, string(out))
+		}
+	}
+
 	return nil
 }
 
-- 
2.51.2