Add ref selector dropdown to create mr(or branch) from issue modal

Rinku Crequested to merge
gitlab-community/gitlab-org/gitlab:rc_add_ref_selector_to_create_mr_from_issue_modal into master

What does this MR do and why?

  1. Adds ref_selector component to modal for creating mr/branch from issue to make it easier to select branches or tags without having to leave the page.
  2. Updates the button labels on create merge request modal to say Target Branch and Source branch name instead of saying Source (branch or tag) and Branch name previously which was really confusing since Source branch was actually a target branch while creating the MR.
  3. Allow user to select branches only while doing create mr flow and allow branches and tags both while doing create branch flow. Previously using tag name to create merge request would cause error since tags cannot be used as source or target for creating merge request.

References

#581851

Screenshots or screen recordings

Before After

CREATE MR FLOW

before_create_mr.png

CREATE BRANCH FLOW

before_create_branch.png

BEFORE CREATE MR FLOW VIDEO(WITH TAG NAME)

before_create_mr_using_tag.mov

CREATE MR FLOW

after_create_mr.png

CREATE BRANCH FLOW

after_create_branch.png

AFTER CREATE MR FLOW

after_create_mr_vid.mov

How to set up and validate locally

  1. Checkout branch and run gdk locally.
  2. Go to any project issue and click Create merge request or Create branch buttons.
  3. Notice the new dropdown selector for branch and updated labels for input fields.

Merge request reports