make cleaning of target directory optional

goldsmith.go

@@ -21,11 +21,13 @@ type Goldsmith struct {
 	fileFilters []Filter
 	fileCache   *cache
 
+	clean bool
+
 	errors []error
 	mutex  sync.Mutex
 }
 
-// Begin starts a chain, reading the files located in sourceDir as input.
+// Begin starts a chain, reading the files located in the source directory as input.
 func Begin(sourceDir string) *Goldsmith {
 	goldsmith := &Goldsmith{
 		sourceDir:     sourceDir,
@@ -43,6 +45,12 @@ func (goldsmith *Goldsmith) Cache(cacheDir string) *Goldsmith {
 	return goldsmith
 }
 
+// Clean enables or disables removal of leftover files in the target directory.
+func (goldsmith *Goldsmith) Clean(clean bool) *Goldsmith {
+	goldsmith.clean = clean
+	return goldsmith
+}
+
 // Chain links a plugin instance into the chain.
 func (goldsmith *Goldsmith) Chain(plugin Plugin) *Goldsmith {
 	goldsmith.contextHasher.Write([]byte(plugin.Name()))
@@ -107,7 +115,10 @@ export:
 		goldsmith.exportFile(file)
 	}
 
+	if goldsmith.clean {
 		goldsmith.removeUnreferencedFiles()
+	}
+
 	return goldsmith.errors
 }