cli/config: Add a helper to resolve a file within the config dir

Signed-off-by: Ian Campbell <ijc@docker.com>

cli/config/config.go

@@ -46,6 +46,11 @@ func SetDir(dir string) {
 	configDir = dir
 }
 
+// Path returns the path to a file relative to the config dir
+func Path(p ...string) string {
+	return filepath.Join(append([]string{Dir()}, p...)...)
+}
+
 // LegacyLoadFromReader is a convenience function that creates a ConfigFile object from
 // a non-nested reader
 func LegacyLoadFromReader(configData io.Reader) (*configfile.ConfigFile, error) {

cli/config/config_test.go

@@ -548,3 +548,17 @@ func TestLoadDefaultConfigFile(t *testing.T) {
 
 	assert.Check(t, is.DeepEqual(expected, configFile))
 }
+
+func TestConfigPath(t *testing.T) {
+	oldDir := Dir()
+
+	SetDir("dummy1")
+	f1 := Path("a", "b")
+	assert.Equal(t, f1, filepath.Join("dummy1", "a", "b"))
+
+	SetDir("dummy2")
+	f2 := Path("c", "d")
+	assert.Equal(t, f2, filepath.Join("dummy2", "c", "d"))
+
+	SetDir(oldDir)
+}