Deliver module releases to full-tag pages

internal/git/source.go

@@ -30,6 +30,20 @@ type TaggedSource struct {
 	TagObjectType string
 }
 
+// CaptureHead records the checkout commit before identity derived from files
+// in that commit is inspected.
+func CaptureHead(ctx context.Context, repositoryDir string) (string, error) {
+	head, err := run(ctx, repositoryDir, nil, "rev-parse", "--verify", "HEAD^{commit}")
+	if err != nil {
+		return "", fmt.Errorf("read checkout HEAD: %w", err)
+	}
+	head = strings.TrimSpace(head)
+	if !validObjectID(head) {
+		return "", fmt.Errorf("Git returned an invalid checkout commit %q", head)
+	}
+	return head, nil
+}
+
 // InspectTaggedSource reads the local HEAD, worktree state, and selected tag.
 // Both lightweight historical tags and annotated tags are supported.
 func InspectTaggedSource(ctx context.Context, repositoryDir, tag string) (TaggedSource, error) {