RFR: cli: rework git-backport

[Christoph Langer]

On Fri, 19 Feb 2021 14:21:05 GMT, Robin Westberg <rwestberg at openjdk.org> wrote:

>> Hi all,
>> 
>> please review this patch that reworks how `git-backport` functions. `git-backport` is now much smaller (and more focused) than it used to be and now composes much better with other Skara CLI tools like `git-pr-create`. `git-backport` now simply fetches a commit from a remote repository and cherry-picks the fetched commit on top of the current branch (without committing). `git-backport` then finally makes a commit with the proper backport commit message (a commit message of the form `Backport <HASH>`).
>> 
>> The tool `git-backport` is now meant to be used in combination with `git-pr-create`, `git-pr-set` and `git-pr-integrate`. The following example shows how a commit can be backported, a pull request created, marking the pull request as clean and then finally integrating the pull request:
>> 
>> $ git checkout -b backport-5a01c3d68ac2
>> $ git backport --from=openjdk/jdk 5a01c3d68ac22b7ee6f0746405a9bdef43281cb7
>> $ git pr create
>> $ sleep 15 # give the bots some time to work
>> $ git pr set --clean
>> $ sleep 15 # allow the bots to do some more work
>> $ git pr integrate
>> $ git checkout -
>> 
>> All (or parts) of the above can of course be wrapped into a [git alias](https://git-scm.com/book/en/v2/Git-Basics-Git-Aliases) for those that don't like to type. The following show an example alias defined in `~/.gitconfig`:
>> 
>> [alias]
>> bp = "!f() { \
>>         git checkout -b backport-$1 && \
>>         git backport --from=openjdk/jdk $1 && \
>>         git pr create; \
>>       }; f"
>> 
>> A user can then simply run `git bp 5a01c3d68ac22b7ee6f0746405a9bdef43281cb7`.
>> 
>> The `--from` parameter to `git-backport` is configurable, so a user who most likely often backports from [openjdk/jdk](https://github.com/openjdk/jdk) can run the following to never have to set `--from` on the command-line:
>> 
>> $ git config --global backport.from https://github.com/openjdk/jdk
>> 
>> Note that `git-backport` only requires a personal access token (PAT) in the case when the `--from` option contains a simple repository name, for example `jdk`. In all other cases there is no need for a PAT, making the command accessible for those who are not using PATs. 
>> 
>> Testing:
>> - [x] Manual testing on Linux x64
>> 
>> Thanks,
>> Erik
>
> Looks good!

Cool. Looking forward to this being integrated. When will the /backport comment be enabled?

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PR: https://git.openjdk.java.net/skara/pull/1025