Add info about adding the project variable when triggering

README.md

@@ -66,17 +66,21 @@ To add a new trigger for another project:
 1. Go to the project you will be triggering from and add a secret variable
    named `DOCS_TRIGGER_TOKEN` with the value of the trigger you copied from the
    previous step.
-1. Add the following job to the project's `.gitlab-ci.yml`:
+1. Add the following job to the project's `.gitlab-ci.yml`, where you should
+   replace the `PROJECT` variable's value with the name of the project the
+   trigger is running from, for example `ce`, `ee`, `omnibus`, `runner`, etc.:
     ```yaml
     # Trigger docs build
     # https://gitlab.com/gitlab-com/doc-gitlab-com/blob/master/README.md#deployment-process
     trigger_docs:
+      variables:
+        GIT_STRATEGY: none
       before_script: []
       cache: {}
       artifacts: {}
       script:
-        - "curl -X POST -F token=${DOCS_TRIGGER_TOKEN} -F ref=master https://gitlab.com/api/v3/projects/38069/trigger/builds"
+        - "curl -X POST -F token=${DOCS_TRIGGER_TOKEN} -F ref=master -F variables[PROJECT]=ce https://gitlab.com/api/v3/projects/38069/trigger/builds"
       only:
         - master
     ```