lack information about regex restriction

Summary

Gitlab has problems with informing user about regex restriction. When You set commit message regex and branch name regex You can meet several wrong gitlab errors:

  1. When Merge Request is created from the Issue level, if branch name does not fit the name regexp, it just pops up an error. Error doesn't mention regex at all.
  2. When you create a commit via Web IDE and commit message does not fit regex gitlab also doesn't inform you about regexp but screams that branch has changed since the last edition, which is very confusing.
  3. The last case is when you try to merge MR and squash commits, gitlab shouts there is the problem with commit message.

Steps to reproduce

Case 1:

  1. Set project with Commit message regex restriction and branch name regex restriction.
  2. Make an Issue and try to create MR and branch from issue level. Of course, the branch name you enter cannot satisfy regex.

Case 2:

  1. Make Merge Request.
  2. Open web IDE, make changes.
  3. Try to commit with invalid commit message. You will get error that branch has changed since the last edition.

Case 3:

  1. Try to merge MR with squashed commits, gitlab shouts there is the problem with commit message.

What is the current bug behavior?

You have wrong gitlab allerts without informations about Regex.

What is the expected correct behavior?

Gitlab informs You when you are trying to make branch/commit with invalid regex.