Update git-flow to 1.12.3
Updated git flow to the latest stable release 1.12.3.
- Explicitly get the default values from the system and global config.
Test Plan: Created a test Git repository and tested a few Git Flow commands all of which worked as expected.
Reviewers: Triage Team, JoshStrobl
Reviewed By: Triage Team, JoshStrobl
Differential Revision: https://dev.getsol.us/D6406