add description about "commit" type

Author: yp05327

templates/repo/branch_dropdown.tmpl

@@ -1,8 +1,8 @@
 {{/* Attributes:
 * ContainerClasses
 * Repository
-* CurrentRefType: eg. "branch", "tag"
-* CurrentRefShortName: eg. "master", "v1.0"
+* CurrentRefType: eg. "branch", "tag", "commit"
+* CurrentRefShortName: eg. "master", "v1.0", "abcdef0123"
 * CurrentTreePath
 * RefLinkTemplate: redirect to the link when a branch/tag is selected
 * RefFormActionTemplate: change the parent form's action when a branch/tag is selected