Merge branch '7500-use-current-ce-ee-merge-base' into 'master'

Use the current merge base between CE MR and EE MR

See merge request gitlab-org/gitlab-ee!7278

scripts/ee_specific_check/ee_specific_check.rb

@@ -33,8 +33,8 @@ module EESpecificCheck
     ce_fetch_head = fetch_remote_ce_branch
     ee_fetch_head = head_commit_sha
     ce_fetch_base = run_git_command("merge-base canonical-ce/master #{ce_fetch_head}")
-    ce_merge_base = run_git_command("merge-base canonical-ce/master canonical-ee/master")
     ee_fetch_base = run_git_command("merge-base canonical-ee/master HEAD")
+    ce_merge_base = run_git_command("merge-base #{ce_fetch_head} #{ee_fetch_head}")
 
     ce_updated_head =
       find_ce_compare_head(ce_fetch_head, ce_fetch_base, ce_merge_base)