Add docs info to dependency.go

cmd/helm/dependency.go

@@ -61,6 +61,20 @@ The 'repository' URL should point to a Chart Repository. Helm expects that by
 appending '/index.yaml' to the URL, it should be able to retrieve the chart
 repository's index. Note: 'repository' cannot be a repository alias. It must be
 a URL.
+
+Starting from 2.2.0, repository can be defined as the path to the directory of
+the dependency charts stored locally. The path should start with a prefix of
+"file://". For example,
+
+    # requirements.yaml
+    dependencies:
+    - name: nginx
+      version: "1.2.3"
+      repository: "file://../dependency_chart/nginx"
+
+If the dependency chart is retrieved locally, it is not required to have the
+repository added to helm by "helm add repo". Version matching is also supported
+for this case.
 `
 
 const dependencyListDesc = `