Changing the default bar lines

Default bar lines can be changed when re-defined in a score context.

\version "2.24"

% http://lsr.di.unimi.it/LSR/Item?id=964
%%=> http://lists.gnu.org/archive/html/lilypond-user/2014-03/msg00126.html
%%=> http://lilypond.1069038.n5.nabble.com/Changing-the-default-end-repeat-bracket-tc169357.html

\layout {
  \context {
    \Score
    %% Changing the defaults from engraver-init.ly
    measureBarType = "!"
    startRepeatBarType = "[|:"
    endRepeatBarType = ":|]"
    doubleRepeatBarType = ":|][|:"
  }
} 

%% example:
{ 
  c'1
  \repeat volta 2 { \repeat unfold 2 c' }
  \repeat volta 2 { \repeat unfold 2 c' }
  \alternative { 
    { c' } 
    { 
      %% v2.18 workaround
      \once\override Score.VoltaBracket.shorten-pair = #'(1 . -1)
      c' 
    } 
  }
  \bar "|."
}