In bug 1129594 we want to add to allthethings.json the branch names that are used for sendchanges. Unfortunately, for mozharness jobs, this cannot be easily be discovered. adusca manages to create a patch with some hardcoding to extract the info (attachment 8562079 [details] [diff] [review]), however, too many hard-codes were needed. I think that if we had a module to calculate sendchange branch names that we could easily drop into braindump (or make dump_allthethings.py fetch it) we would be able to calculate the branch names.

Build jobs that don't go through Mozharness have a "SendChangeStep" (e.g. [1]) step in their buildbot configuration. Mozharness jobs (e.g. [2]), on the other hand, do their sendchanges on the slave side (either through [3] or [4], depending on the job). These functions depend on a lot of state variables and cannot be easily exported. For example, they read (at least) the following configuration keys:'stage_platform', 'branch_uses_per_checkin_strategy', 'debug_build', 'enable_talos_sendchange','enable_unittest_sendchange', 'nightly_build','pgo_build', 'pgo_platforms' [1] https://github.com/petermoore/build-buildbotcustom/blob/956b38c2f2c05d43bf960cd15ac02ad3c646a165/process/factory.py#L2037 [2] https://hg.mozilla.org/build/buildbotcustom/file/c1e8ea50075d/misc.py#l686 [3] https://github.com/mozilla/build-mozharness/blob/0a4f14aa76bb3419b9fe5ad28105dd9796c4d4c5/mozharness/mozilla/building/buildbase.py#L1521 [4] https://github.com/mozilla/build-mozharness/blob/master/mozharness/mozilla/buildbot.py#L142

we don't use sendchanges anymore