Fix issues with IDE commit to new branch

What does this MR do?

This MR resolves #233423 (closed), but also fixes a few other significant issues when committing to a new branch in the Web IDE.

Screenshots (strongly suggested)

Before:

• After committing you'll notice the Route still has the old branch.
• This causes major issues when comparing future file changes.

After:

• You'll notice that the route now has the new branch and future file changes work 🎉

Before	After	After (start new MR also works)
20210113_bug_commit_to_new_branch	20210113_fix_commit_new_branch	20210113_fix_commit_new_branch_to_mr

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

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

Related to #233423 (closed)