Vendor dependencies for compose-file.

Signed-off-by: Daniel Nephin <dnephin@docker.com>

vendor/github.com/aanand/compose-file/interpolation/interpolation.go

@@ -0,0 +1,89 @@
+package interpolation
+
+import (
+	"fmt"
+
+	"github.com/aanand/compose-file/template"
+	"github.com/aanand/compose-file/types"
+)
+
+func Interpolate(config types.Dict, section string, mapping template.Mapping) (types.Dict, error) {
+	out := types.Dict{}
+
+	for name, item := range config {
+		if item == nil {
+			out[name] = nil
+			continue
+		}
+		interpolatedItem, err := interpolateSectionItem(name, item.(types.Dict), section, mapping)
+		if err != nil {
+			return nil, err
+		}
+		out[name] = interpolatedItem
+	}
+
+	return out, nil
+}
+
+func interpolateSectionItem(
+	name string,
+	item types.Dict,
+	section string,
+	mapping template.Mapping,
+) (types.Dict, error) {
+
+	out := types.Dict{}
+
+	for key, value := range item {
+		interpolatedValue, err := recursiveInterpolate(value, mapping)
+		if err != nil {
+			return nil, fmt.Errorf(
+				"Invalid interpolation format for %#v option in %s %#v: %#v",
+				key, section, name, err.Template,
+			)
+		}
+		out[key] = interpolatedValue
+	}
+
+	return out, nil
+
+}
+
+func recursiveInterpolate(
+	value interface{},
+	mapping template.Mapping,
+) (interface{}, *template.InvalidTemplateError) {
+
+	switch value := value.(type) {
+
+	case string:
+		return template.Substitute(value, mapping)
+
+	case types.Dict:
+		out := types.Dict{}
+		for key, elem := range value {
+			interpolatedElem, err := recursiveInterpolate(elem, mapping)
+			if err != nil {
+				return nil, err
+			}
+			out[key] = interpolatedElem
+		}
+		return out, nil
+
+	case []interface{}:
+		out := make([]interface{}, len(value))
+		for i, elem := range value {
+			interpolatedElem, err := recursiveInterpolate(elem, mapping)
+			if err != nil {
+				return nil, err
+			}
+			out[i] = interpolatedElem
+		}
+		return out, nil
+
+	default:
+		return value, nil
+
+	}
+
+}