Extract issue id from branch name

.vimrc

" get reference for the current issue from git branch name
" assumes your branch name looks like 1337-fixing-a-lot-of-stuff
"
function GitBranchIssue(fixes)
  let current_branch = system("git rev-parse --abbrev-ref HEAD")
  let ref = substitute(current_branch, '^.\+\/\(\d\+\).\+$', '\1', '')
  if a:fixes == 'true'
    let prefix = 'fixes'
  else
    let prefix = 'refs'
  endif
  return prefix . ' #' . ref
endfunction
iab REFS <C-R>=GitBranchIssue('false')<CR>
iab FIXES <C-R>=GitBranchIssue('true')<CR>