Resolve "WebIDE Default Commit options"

What does this MR do?

Closes #51470 (closed)

Screenshots (green text has been post-added to the images to explain the particular scenario):

	header
Default branch (no matter the existence of an MR), user has write access for the branch
Default branch (no matter the existence of an MR), user has NO write access for the branch
Protected branch (no matter existence of an MR), user has NO write access for the branch
Protected branch, user has write access for the branch (no MR)
Non-default branch (no MR)
Non-default branch (existing MR)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry for user-facing changes, or community contribution. Check the link for other scenarios.
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance and testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Closes #51470 (closed)