Update README with instructions to fetch MRs from origin (Fixes #370)

README.md

@@ -60,14 +60,14 @@ To enable this functionality, a user should be set up on GitLab, with GitLab 'De
 1. In the *Source Code Management* section:
     1. Click *Git*
     2. Enter your *Repository URL* (e.g.: ``[email protected]:group/repo_name.git``)
-      * In the Advanced settings, set its *Name* to ``origin``
+      * In the Advanced settings, set its *Name* to ``origin`` and its *refspec* to ``+refs/heads/*:refs/remotes/origin/* +refs/merge-requests/*/head:refs/remotes/origin/merge-requests/*``
     3. To be able to merge from forked repositories:  <br/>**Note:** this requires [configuring communication to the GitLab server](#configuring-access-to-gitlab)
       * Add a second repository with:
         * *URL*: ``${gitlabSourceRepoURL}`` 
         * *Name* (in Advanced): ``${gitlabSourceRepoName}``
     4. In *Branch Specifier* enter:
       * For single-repository setups: ``origin/${gitlabSourceBranch}``
-      * For forked repository setups: ``${gitlabSourceRepoName}/${gitlabSourceBranch}``
+      * For forked repository setups: ``merge-requests/${gitlabMergeRequestIid}``
     5. In *Additional Behaviours*:
         * Click the *Add* drop-down button.
         * Select *Merge before build* from the drop-down.