requestdecorator: repurpose the package and rename to useragent

Signed-off-by: Tibor Vass <tibor@docker.com>

useragent/useragent_test.go

@@ -0,0 +1,31 @@
+package useragent
+
+import "testing"
+
+func TestVersionInfo(t *testing.T) {
+	vi := VersionInfo{"foo", "bar"}
+	if !vi.isValid() {
+		t.Fatalf("VersionInfo should be valid")
+	}
+	vi = VersionInfo{"", "bar"}
+	if vi.isValid() {
+		t.Fatalf("Expected VersionInfo to be invalid")
+	}
+	vi = VersionInfo{"foo", ""}
+	if vi.isValid() {
+		t.Fatalf("Expected VersionInfo to be invalid")
+	}
+}
+
+func TestAppendVersions(t *testing.T) {
+	vis := []VersionInfo{
+		{"foo", "1.0"},
+		{"bar", "0.1"},
+		{"pi", "3.1.4"},
+	}
+	v := AppendVersions("base", vis...)
+	expect := "base foo/1.0 bar/0.1 pi/3.1.4"
+	if v != expect {
+		t.Fatalf("expected %q, got %q", expect, v)
+	}
+}