fix: respect COMPOSE_FILE when loading compose files

Final part of coop-cloud/go-abra#57.

config/app.go

@@ -225,22 +225,35 @@ func GetAppStatuses(appFiles AppFiles) (map[string]string, error) {
 	return statuses, nil
 }
 
-// GetAppComposeFiles retrieves a compose specification for a recipe. This
-// specification is the result of a merge of all the compose.**.yml files in
-// the recipe repository.
-func GetAppComposeFiles(recipe string, appEnv AppEnv) (*composetypes.Config, error) {
-	pattern := fmt.Sprintf("%s/%s/compose**yml", APPS_DIR, recipe)
-	composeFiles, err := filepath.Glob(pattern)
-	if err != nil {
-		return &composetypes.Config{}, err
+// GetAppComposeFiles gets the list of compose files for an app which should be
+// merged into a composetypes.Config while respecting the COMPOSE_FILE env var.
+func GetAppComposeFiles(recipe string, appEnv AppEnv) ([]string, error) {
+	if _, ok := appEnv["COMPOSE_FILE"]; !ok {
+		pattern := fmt.Sprintf("%s/%s/compose**yml", APPS_DIR, recipe)
+		composeFiles, err := filepath.Glob(pattern)
+		if err != nil {
+			return composeFiles, err
+		}
+		return composeFiles, nil
 	}
 
-	opts := stack.Deploy{Composefiles: composeFiles}
+	var composeFiles []string
+	composeFileEnvVar := appEnv["COMPOSE_FILE"]
+	for _, file := range strings.Split(composeFileEnvVar, ":") {
+		path := fmt.Sprintf("%s/%s/%s", APPS_DIR, recipe, file)
+		composeFiles = append(composeFiles, path)
+	}
+	return composeFiles, nil
+}
+
+// GetAppComposeConfig retrieves a compose specification for a recipe. This
+// specification is the result of a merge of all the compose.**.yml files in
+// the recipe repository.
+func GetAppComposeConfig(recipe string, opts stack.Deploy, appEnv AppEnv) (*composetypes.Config, error) {
 	compose, err := loader.LoadComposefile(opts, appEnv)
 	if err != nil {
 		return &composetypes.Config{}, err
 	}
-
 	return compose, nil
 }