Add support for ref parameter to get raw file API (#14602)

Fix #14597

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

templates/swagger/v1_json.tmpl

@@ -7845,6 +7845,12 @@
             "name": "filepath",
             "in": "path",
             "required": true
+          },
+          {
+            "type": "string",
+            "description": "The name of the commit/branch/tag. Default the repository’s default branch (usually master)",
+            "name": "ref",
+            "in": "query"
           }
         ],
         "responses": {