fix: file save start_branch as a body attribute

nickbroon · JohnVillalovos · commit 1001d934e8c3 · 2026-01-20T06:47:04.000-08:00
Passing `start_branch` as kwargs results in it being passed as query argument to the API: ``` send: b'PUT /api/v4/projects/12345678/repository/files/readme.txt?start_branch=main send: b'{"file_path": "readme.txt", "branch": "new_branch", "content": "Modified contents", "commit_message": "File was modified for this new branch"}' ``` which results in error being returned: ``` {"message":"You can only create or edit files when you are on a branch"} ``` It should instead be sent a body attribute, which succeeds in creating the branch during the save. To be sent as body attribute it must be specified as concrete function argument and class attribute instead of just using kwargs Closes: #3318
diff --git a/gitlab/v4/objects/files.py b/gitlab/v4/objects/files.py
@@ -29,6 +29,7 @@ class ProjectFile(SaveMixin, ObjectDeleteMixin, RESTObject):
     file_path: str
     manager: ProjectFileManager
     content: str  # since the `decode()` method uses `self.content`
+    start_branch: str | None = None
 
     def decode(self) -> bytes:
         """Returns the decoded content of the file.
@@ -41,7 +42,11 @@ def decode(self) -> bytes:
     # NOTE(jlvillal): Signature doesn't match SaveMixin.save() so ignore
     # type error
     def save(  # type: ignore[override]
-        self, branch: str, commit_message: str, **kwargs: Any
+        self,
+        branch: str,
+        commit_message: str,
+        start_branch: str | None = None,
+        **kwargs: Any,
     ) -> None:
         """Save the changes made to the file to the server.
 
@@ -50,6 +55,7 @@ def save(  # type: ignore[override]
         Args:
             branch: Branch in which the file will be updated
             commit_message: Message to send with the commit
+            start_branch: Name of the branch to start the new branch from
             **kwargs: Extra options to send to the server (e.g. sudo)
 
         Raises:
@@ -58,6 +64,7 @@ def save(  # type: ignore[override]
         """
         self.branch = branch
         self.commit_message = commit_message
+        self.start_branch = start_branch
         self.file_path = utils.EncodedId(self.file_path)
         super().save(**kwargs)
 
