Track all release branches

[Totktonada]

In tarantool we push a commit to master branch first and than cherry-pick it to release branches such as 2.5, 2.4, ..., 1.10.

It would be great to track updates of all release branches and update a corresponding documentation issue with a comment like:

Pushed to 2.4 in <commit-url>.

We should also reopen the documentation issue if it closed at the moment.

It would be good to provide four-digit version numbers for such updates.

It should be useful for tarantool/doc#1415

Details

How to match a documentation request with an issue within the documentation repository? Considering the service tends to be stateless (it is my guess, I didn't look deeply) I would just traverse over documentation issue using GitHub API and match by a title. A title should be quite unique. There is no such guarantee, but I guess collisions will be very rare, so we can fix wrong automatic comments manually (delete the comment and open a new issue). Reasonable runtime caching can be used to speed up the search (a cache within a process memory).

What with comminting an issue flow (as against placind a documentation comment within a commit message)? It seems it can be complicated. At least it requires parsing of keywords, which closes an issue, and performing an additional request to see whether the issue has a documentation request. But it seems to be doable and will work if the issue is closed from a commit message.