go.mod: update gitlab dep to v0.30.1

Releases after github.com/xanzy/go-gitlab@v0.31.0 introduce breaking
changes to the NewClient call.

Addresses #94

vendor/github.com/docker/distribution/reference/helpers.go

@@ -0,0 +1,42 @@
+package reference
+
+import "path"
+
+// IsNameOnly returns true if reference only contains a repo name.
+func IsNameOnly(ref Named) bool {
+	if _, ok := ref.(NamedTagged); ok {
+		return false
+	}
+	if _, ok := ref.(Canonical); ok {
+		return false
+	}
+	return true
+}
+
+// FamiliarName returns the familiar name string
+// for the given named, familiarizing if needed.
+func FamiliarName(ref Named) string {
+	if nn, ok := ref.(normalizedNamed); ok {
+		return nn.Familiar().Name()
+	}
+	return ref.Name()
+}
+
+// FamiliarString returns the familiar string representation
+// for the given reference, familiarizing if needed.
+func FamiliarString(ref Reference) string {
+	if nn, ok := ref.(normalizedNamed); ok {
+		return nn.Familiar().String()
+	}
+	return ref.String()
+}
+
+// FamiliarMatch reports whether ref matches the specified pattern.
+// See https://godoc.org/path#Match for supported patterns.
+func FamiliarMatch(pattern string, ref Reference) (bool, error) {
+	matched, err := path.Match(pattern, FamiliarString(ref))
+	if namedRef, isNamed := ref.(Named); isNamed && !matched {
+		matched, _ = path.Match(pattern, FamiliarName(namedRef))
+	}
+	return matched, err
+}