Replace textbox by a dropdown list for selecting branch when you create a branch from an issue
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### Proposal
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Replace textbox by a dropdown list for selecting branch when you create a branch from an issue.
In our team, we create our branch and our MR directly from our issue.
Currently, it is a textbox to set the source branch. Just a basic validation.
{width=228 height=279}
For us, it isn't easy to use this textbox.
The goal is to replace it by a dropdown list like in MR for example:
{width=333 height=174}
or at minimum, remove the "false" prefilled value or replace it by a "true" prefilled value.
When I say "false", I means we can not selected the prefilled value, like isn't really filled.
It is a gif to show I can not selected the prefilled value to replace it easily:

Current Gitlab version: GitLab Enterprise Edition v17.6.5-ee
issue