Find the EE branch by searching the branches

This uses a similar approach in ee_specific_check.rb

lib/gitlab/ee_compat_check.rb

@@ -138,16 +138,24 @@ module Gitlab
 
     def ee_branch_presence_check!
       ee_remotes.keys.each do |remote|
-        [ce_branch, ee_branch_prefix, ee_branch_suffix].each do |branch|
-          _, status = step("Fetching #{remote}/#{branch}", %W[git fetch #{remote} #{branch}])
+        output, _ = step(
+          "Searching #{remote}",
+          %W[git ls-remote #{remote} *#{minimal_ee_branch_name}*])
+
+        branches =
+          output.scan(%r{(?<=refs/heads/|refs/tags/).+}).sort_by(&:size)
+
+        next if branches.empty?
+
+        branch = branches.first
+
+        step("Fetching #{remote}/#{branch}", %W[git fetch #{remote} #{branch}])
 
-          if status.zero?
         @ee_remote_with_branch = remote
         @ee_branch_found = branch
+
         return true
       end
-        end
-      end
 
       puts
       puts ce_branch_doesnt_apply_cleanly_and_no_ee_branch_msg
@@ -271,6 +279,10 @@ module Gitlab
       @ee_patch_full_path ||= patches_dir.join(ee_patch_name)
     end
 
+    def minimal_ee_branch_name
+      @minimal_ee_branch_name ||= ce_branch.sub(/(\Ace\-|\-ce\z)/, '')
+    end
+
     def patch_name_from_branch(branch_name)
       branch_name.parameterize << '.patch'
     end