Submodule build process hangs when using branch as submodule

Issue Summary

Submodule checkout fails if a branch is set in .gitmodules.

This is reproducible on Data Center: (yes) / (no)

Steps to Reproduce

1. Create a plan with Master as Main module and Branch Submodule from same repository(BB)
2. Build the plan

Expected Results

Build to be completed successfully with submodule

Actual Results

submodule checkout fails and Build hangs.

The below exception is thrown in the atlassian-bamboo-agent.log file:

 Checkout to revision de3cbdf7aab338f153be24576b7e467b68b5791b has failed.command ['D:\Development Tools\Git\cmd\git.exe' submodule update --init --recursive] failed with code 1.

Workaround

Have configured SSH keys between Bamboo Server/Agent and the Repository then run "git submodule update --init --recursive --remote" from a Script Task right after the Checkout is done.