Branching improvements

This MR improves the branching pipeline, it's based on !215 (merged) but excluding commits still in discussion.

requested review from @wlozano

assigned to @daissi

@wlozano What do you think about this selection of commits from !215 (merged)?

approved this merge request

added 1 commit

• 37a78a2f - branch-update-repo: simplify conditions to update the default release in ci-flatdeb-builder

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added 1 commit

• a09c3cae - branch-update-repo: also update the stable default release in ci-flatdeb-builder

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added 1 commit

• 56bde794 - branch-update-repo: also update the stable default release in ci-flatdeb-builder

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added 1 commit

• fba6d23b - branch-update-repo: also update the stable default release in ci-flatdeb-builder

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resolved all threads

enabled an automatic merge when all merge checks for fba6d23b pass

merged