When your pull request breaks an external project we test in our CI and you have prepared a branch with the fix, you can add an "overlay" to your pull request to test it with the adapted version of the external project.
An overlay is a file which defines where to look for the patched
version so that testing is possible. This is done by calling the
overlay command for each project with the project name (as used in
the variables in ci-basic-overlay.sh), the
location of your fork and the branch containing the patch on your
fork.
Moreover, the file contains very simple logic to test the pull request number or branch name and apply it only in this case.
The name of your overlay file should start with a five-digit pull request
number, followed by a dash, anything (for instance your GitHub nickname
and the branch name), then a .sh extension ([0-9]{5}-[a-zA-Z0-9-_]+.sh).
Example: 13128-SkySkimmer-noinstance.sh containing
if [ "$CI_PULL_REQUEST" = "13128" ] || [ "$CI_BRANCH" = "noinstance" ]; then
overlay elpi https://github.com/SkySkimmer/coq-elpi noinstance
fi
(CI_PULL_REQUEST and CI_BRANCH are set in ci-common.sh)
We suggest you use the convention of identical branch names for the
Coq branch and the CI project branch used in the overlay. For example,
if your Coq PR is coming from the branch more_efficient_tc, and that
breaks ltac2, we suggest you create a ltac2 overlay with a branch
named more_efficient_tc.