Design & Implement a script that will automatically generate a release branch

[minosgalanakis]

Suggested enhancement

This task contains the requirement to build a script that will automatically generate release branches. The script should aimed to be executed in the restricted repositories and be capable of:

• Fetch public branches and capture the hashes of the input
• Merging -restricted branches onto public ones
• Determine the name convention of the release branches based as described in therelease process
• If the merge is clean it shoud return 0 and the name of the branch that contains the RC. If a merge conflict happens, it should abort the merge and return -1

Optional and good to have features that may be moved to a future issue:

• Cherry pick specific commits on top of the result after the merge.
• Create input sync braches, as described in the release process by moving the submodule pointers for all release inputs.

Mbed TLS needs this because it facilitates release creation and streamlines reviews. It will also enable the nighly CI to test and notify us in case the codebase is broken, ahead of starting a release.