tarantool / tarantool / 12889005472

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github

ci: add action for automatic backporting

This patch adds an action for backporting automatization. Instead of
doing everything with your hands you may now use one the following
workflows for simple cherry-pick cases.

The first option (using labels).
* Add labels `backport/<release to backport to>` to the PR you want to
  backport (e.g for backporting to versions 2.11 and 3.2 add labels
  `backport/3.2` and `backport/2.11`).
* Merge the original pull request.
* Merge the automatically created Pull requests by GitHub-actions bot.

The second option (using command).
* Merge the original pull request.
* Write `/backport <releases to backport to list separated by space...>`
  comment (e.g. `/backport 3.2 3.3`).
* Merge the automatically created Pull requests by GitHub-actions bot.

The bot creates a pull request from
`backport/${target branch}/${pull number}` containing a few cherry picks
with `-x` flag from the original patch/patchset and using the following
title format.

```
[backport ${target minor version}] ${orig pull title}.
```

And the following body format.
```
*(This PR is a backport of #${pull number} to `${target branch}` to a
future `${future release number}`.)*

---

${pull_description}
```

The bot also copies all labels except ones used for backporting. It can
be handy for copying `full-ci`.

In case of merge conflicts the bot notifies you and asks to perform
backporting by yourself:

```
Backport failed for `release/1.0`, because it was unable to cherry-pick
the commit(s).

Please cherry-pick the changes locally and resolve any conflicts.
```

And suggests executing the commands similar to the following.
```bash
git fetch origin release/1.0
git worktree add -d .worktree/backport/release/1.0/8 origin/release/1.0
cd .worktree/backport/release/1.0/8
git switch --create backport/release/1.0/8
git cherry-pick -x 683e9a53b
```

After processing the merge or the command the bot writes a report on the
successfully... (continued)

69665 of 123532 branches covered (56.39%)

102653 of 117490 relevant lines covered (87.37%)

2378418.31 hits per line