ref/refname: Add refname validation

1 files changed, 20 insertions, 0 deletions

diff --git a/ref/refname/tag.go b/ref/refname/tag.go
new file mode 100644
index 00000000..226c0fdd
--- /dev/null
+++ b/ref/refname/tag.go
@@ -0,0 +1,20 @@
+package refname
+
+import "strings"
+
+// Tag checks one tag shorthand and returns its fully-qualified
+// refs/tags/... name.
+func Tag(name string) (string, error) {
+	if strings.HasPrefix(name, "-") || name == "HEAD" {
+		return "", &NameError{Name: name, Reason: "invalid tag name"}
+	}
+
+	full := "refs/tags/" + name
+
+	err := validate(full, 0)
+	if err != nil {
+		return "", err
+	}
+
+	return full, nil
+}