Found piece-wise solution but will continue to look for better answer
Moved to symbolic-ref for `get_git_branch` in all cases
Broke down $PS1 for better readability
Adding test against `is_on_git` for `git branch` based errors
Moved back to working `is_on_git` =)
Added test and caught `get_git_branch` breaking for `git-init` directories
Moved back to working `get_git_branch`
Updated CHANGELOG. This release will fix #4, #5.