Vendor integration dependencies.

integration/vendor/github.com/docker/libcompose/lookup/composable.go

@@ -0,0 +1,25 @@
+package lookup
+
+import (
+	"github.com/docker/libcompose/config"
+)
+
+// ComposableEnvLookup is a structure that implements the project.EnvironmentLookup interface.
+// It holds an ordered list of EnvironmentLookup to call to look for the environment value.
+type ComposableEnvLookup struct {
+	Lookups []config.EnvironmentLookup
+}
+
+// Lookup creates a string slice of string containing a "docker-friendly" environment string
+// in the form of 'key=value'. It loop through the lookups and returns the latest value if
+// more than one lookup return a result.
+func (l *ComposableEnvLookup) Lookup(key, serviceName string, config *config.ServiceConfig) []string {
+	result := []string{}
+	for _, lookup := range l.Lookups {
+		env := lookup.Lookup(key, serviceName, config)
+		if len(env) == 1 {
+			result = env
+		}
+	}
+	return result
+}