GitLab documentation refers users to Rubular for checking regex expressions, however the below expressions for restricting branch names on merge is denied upon merge attempt saying,
GitLab: Branch name does not follow the pattern ‘\A(feature|hotfix|bug)/\S[a-z-]+\z’
Branch name: feature/sort-and-display-assignment-list
Expressions attempted:
\A(feature|hotfix|bug)/\S[a-z-]+\z
(feature|hotfix|bug)/\S[a-z-]+
(feature|hotfix|bug)/[a-z-]+
(feature|hotfix|bug)/
(feature|hotfix|bug)/*
Please refer to this summary example: http://rubular.com/r/ObfIoOve0Q