Issue Summary

"Override branch of a linked repository " option for GIT type repository doesn't show the options to choose the branch inside the repository tab of the plan. 

Also when using the option of Override branch of a linked repository with a new branch name, it does update the value on the GUI. 

Steps to Reproduce

1) Create a GIT Type linked repository in Bamboo ( Bitbucket Cloud repo linked as GIT type repo )
2) Link this repository to a plan in Bamboo
3) Go to the repository tab of the plan and click on the repository
4) Check the section "Override branch of a linked repository"
5) Update the branch name to a new value

Expected Results

1) The branch field is set to the correct branch 

Actual Results

1) The field is empty, as shown below:

2) Also the value which is overriden after saving the repository it gets removed

Workaround

Manually enter the branch name in the checkbox to replace the branch.