Expose the title and upstream branch of a Pull Request build as an env



Continuing the discussion from Retrieving pull request title:

GitHub provides the title of a pull request in the web hook, but it is not currently available.

The same goes for the upstream branch name.

It would be very helpful to expose these values as environmental variables, for use in build configs and notifications.

Please be sure to :heart: this feature request, as that is how the CircleCi product team prioritizes requests.

How to get the pull request upstream branch?
Retrieving pull request title

I have the same requirement for the base branch, since my builds need to perform some operations (like CS checks by instance) only on the diff.
Something like: git diff $CIRCLE_BRANCH..$CIRCLE_BASE_BRANCH | some-cmd