Fix MR target branch select dropdown placement cut-off

What does this MR do?

• Fix target branch select dropdown cut-off when branch names are too long

EE MR: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1748

When we have enough space

When we don't have enough space

When branch names not long enough

Are there points in the code the reviewer needs to double check?

• select2 seems to have some faulty logic with dropdownAutoWidth and not enough options to fix this succinctly(with a placement option for example).

This isn't a regression in the truest sense. But we are going to "call it a regression because the feature went from usable to almost unusable. -- @brycepj, https://gitlab.com/gitlab-org/gitlab-ce/issues/31271#note_28176095"

Why was this MR needed?

When the project has long branch names, the target branch selector on the edit MR page is placed off the screen (outside of the viewport).

Does this MR meet the acceptance criteria?

• Tests
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #31271 (closed)

changed milestone to %9.1

This isn't a regression in the truest sense. But we are going to "call it a regression because the feature went from usable to almost unusable. -- @brycepj, https://gitlab.com/gitlab-org/gitlab-ce/issues/31271#note_28176095"

assigned to @annabeldunstone

@alfredo1 can you please review?

assigned to @alfredo1

@MadLittleMods I'm still seeing the bug with the viewport set to 970px width

assigned to @MadLittleMods

marked the checklist item All builds are passing as completed

@alfredo1 Fixed up, seemed to be only an issue in Safari.

resolved all discussions

added 1 commit

• 640e65ae - Fix MR target branch selector dropdown placement cut-off

Compare with previous version

added 220 commits

• 640e65ae...d031665a - 219 commits from branch master
• 98f4e60c - Fix MR target branch selector dropdown placement cut-off

Compare with previous version

assigned to @alfredo1

@alfredo1 It popped the EE compat check but when making the EE branch, there were no conflicts. I pushed it anyway but currently waiting for the queue to actually get it to appear in the MR branch list (seems to be in the normal branch list), https://gitlab.com/gitlab-org/gitlab-ee/commits/ee-31271-fixmr-target-branch-selector-dropdown EE MR created, https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1748

assigned to @rymai

assigned to @alfredo1

added 176 commits

• 98f4e60c...623eb34f - 175 commits from branch master
• 3584e74e - Fix MR target branch selector dropdown placement cut-off

Compare with previous version

@alfredo1 Friendly ping for review

assigned to @jschatz1

approved this merge request

Does this work? Does't work for me.

@MadLittleMods I would think the solution would be to use GL dropdown because the other dropdowns are GL dropdown.

assigned to @MadLittleMods

@jschatz1 What's wrong with the given screenshot? The dropdown extends as far as it needs to cover that long branch name. Clarified via a chat, all good.

assigned to @jschatz1

resolved all discussions

merged

mentioned in commit 3a2b60f7

mentioned in commit 04e3c36c

Picked into 9-1-stable, will go into 9.1.4