Add support of custom message to merge action of satellite

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Use same code for diff and patch inside MergeAction

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Add merge_commit_message argument for Satellite::MergeAction#merge
MergeRequest#automerge accepts custom message now. MergeRequest#merge_commit_message generate default one

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Use params[:merge_commit_message] in MergeRequestController for automerge

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Add UI for custom Merge request commit message

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Fix mr controller specs

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Tests for accept MR with custom message

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Dont allow merge without commit message

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge branch 'feature/merge_commit_message' of /home/git/repositories/gitlab/gitlabhq