[PATCH i-g-t v1 2/2] CONTRIBUTING: Add explanation how to run CI locally

[Kamil Konieczny]

From: Louis Chauvet <louis.chauvet at bootlin.com>

Currently, the CI runs only after a merge happens. To avoid reverts
because of error in some configurations, add an explanation how to
run it locally with a new file .gitlab-ci-local.yml

This is basing on a project available here:
https://github.com/firecow/gitlab-ci-local

v2: fixed description, dropped .gitlab-ci-local (Kamil)

Signed-off-by: Louis Chauvet <louis.chauvet at bootlin.com>
Signed-off-by: Kamil Konieczny <kamil.konieczny at linux.intel.com>
---
 CONTRIBUTING.md | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 05bb64bf4..6b305aef6 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -135,6 +135,23 @@ Sending Patches
   can help our bug-filing team. When replying, you can cut a message after
   'Known bugs' to keep it in reasonable size.
 
+- When pushing a new series, your series will be build-tested by the CI. It is
+  useful to avoid merging broken stuff. You can run this CI locally by using the
+  project https://github.com/firecow/gitlab-ci-local
+  To install it, please refer to its README (on debian, the package
+  gitlab-ci-local can be used).
+
+  To run it locally, you need to build docker images:
+
+    docker build . -f Dockerfile.build-fedora -t igt-build-fedora:latest
+
+  Now you should be able to run it:
+
+    gitlab-ci-local --file .gitlab-ci-local.yml
+
+  If you want to run a specific stage, you can add it to the command line:
+
+    gitlab-ci-local --file .gitlab-ci-local.yml <stage>
 
 Commit Rights
 -------------
-- 
2.49.0