RFR: Initial implementation of dependent pull requests [v2]

[Erik Helin]

On Fri, 16 Oct 2020 13:34:21 GMT, Robin Westberg <rwestberg at openjdk.org> wrote:

>> This is the initial implementation of the support for creating a follow-up pull request while the first one is still
>> out for review. This will allow having multiple dependent changes out for review simultaneously, which is something
>> that was possible during the hg/webrev era.  To use it, first create a pull request from the first change. In that pull
>> request, issue the `/preintegrate` command. This will publish the current contents to a new branch in the *target*
>> repository named `pr/<username>/<pr-id>`. Now any follow-up work can target this branch instead, which contains the
>> dependent work.  When the first pull request is `/integrate`d, any follow-up pull requests will automatically be
>> retargeted to the original target branch. It will not be possible to `/integrate` the follow-up pull request until the
>> first one has been integrated.
>
> Robin Westberg has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update pre-integration target branches automatically

Looks good!

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Marked as reviewed by ehelin (Reviewer).

PR: https://git.openjdk.java.net/skara/pull/886