Fuel/Soft Code Freeze

Soft Code Freeze (SCF) is a time-based milestone in the Fuel release cycle that marks the point after which only High and Critical bug fixes are allowed in the release branch.

Once SCF is announced:


 * stable branch is created for the release
 * only fixes for High and Critical bugs are allowed in the stable branch
 * commits to the stable branch must follow the backporting process: only propose a stable backport after the fix was merged in the master branch
 * master branch is open for feature development for the next release and for Medium and lower priority bug fixes

Rationale: restricting stable branch to High and Critical bugfixes encourages the team to focus on a smaller number of bugs, and reduces the number of regressions introduced by commits merged into the stable branch.