Move "common/config" common types into cfgtypes.

luci_config/common/cfgtypes/config_set.go

Index: luci_config/common/cfgtypes/config_set.go
diff --git a/luci_config/common/cfgtypes/config_set.go b/luci_config/common/cfgtypes/config_set.go
new file mode 100644
index 0000000000000000000000000000000000000000..b2a61aa9a364dd0256b2f6332fe89f265ba98b47
--- /dev/null
+++ b/luci_config/common/cfgtypes/config_set.go
@@ -0,0 +1,75 @@
+// Copyright 2016 The LUCI Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package cfgtypes
+
+import (
+	"strings"
+)
+
+// ConfigSet is a configuration service Config Set string.
+//
+// A config set consists of a domain and a series of path components:
+// domain/target/refs...
+//
+//	- Service config sets are config sets in the "services" domain, with the
+//	  service name as the target.
+//	- Project config sets are config sets in the "projects" domain. The target
+//	  is the project name.
+type ConfigSet string
+
+// ServiceConfigSet returns the name of a config set for the specified service.
+func ServiceConfigSet(name string) ConfigSet { return ConfigSet("services/" + name) }
+
+// ProjectConfigSet returns the config set for the specified project.
+func ProjectConfigSet(name ProjectName) ConfigSet { return RefConfigSet(name, "") }
+
+// RefConfigSet returns the config set for the specified project and ref. If ref
+// is empty, this will equal the ProjectConfigSet value.
+func RefConfigSet(name ProjectName, ref string) ConfigSet {
+	if ref == "" {
+		return ConfigSet("projects/" + string(name))
+	}
+	return ConfigSet(strings.Join([]string{"projects", string(name), ref}, "/"))
+}
+
+// Split splits a ConfigSet into its domain, target, and ref components.
+func (cs ConfigSet) Split() (domain, target, ref string) {
+	switch p := strings.SplitN(string(cs), "/", 3); len(p) {
+	case 1:
+		return p[0], "", ""
+	case 2:
+		return p[0], p[1], ""
+	default:
+		return p[0], p[1], p[2]
+	}
+}
+
+// SplitProject splits a project-rooted config set (projects/<name>[/...]) into
+// its project name, project config set, and ref components.
+//
+// For example, "projects/foo/bar/baz" is a config set that belongs to project
+// "foo". It will be parsed into:
+//	- project: "foo"
+//	- projectConfigSet: "projects/foo"
+//	- ref: "bar/baz"
+//
+// If configSet is not a project config set, empty strings will be returned.
+func (cs ConfigSet) SplitProject() (project ProjectName, projectConfigSet ConfigSet, ref string) {
+	parts := strings.SplitN(string(cs), "/", 3)
+	if len(parts) < 2 || parts[0] != "projects" {
+		// Not a project config set, so neither remaining Authority can access.
+		return
+	}
+
+	// The project is the first part.
+	project = ProjectName(parts[1])
+
+	// Re-assemble the project part of the config set ("projects/foo").
+	projectConfigSet = cs[:len("projects/")+len(project)]
+	if len(parts) > 2 {
+		ref = parts[2]
+	}
+	return
+}