[CDash] GitHub Status API support

[Cristian Morales Vega]

Hi,

Currently when I push to GitHub it notifies my Jenkins instance. I
want Jenkins to run a ctest script, which will include

set(CTEST_UPDATE_VERSION_ONLY ON)
ctest_update()

And submit the results to CDash.
..and I would like CDash to tell GitHub about what it finds using its
Status API (https://developer.github.com/v3/repos/statuses/).

There is a simple way to do this?

I know about https://cmake.org/cmake/help/latest/variable/CTEST_CHANGE_ID.html,
but I have been unable to find too much documentation about it. It
let's me "pass arbitrary information" which could for example be used
"to post comments on your pull request". How "arbitrary" becomes "pull
request ID", and whether I can make it mean "git commit" is unclear.

Regards.