rit = 
  \tweak bound-details.left.text #"rit. "
  \startTextSpan 

rall = 
  \tweak bound-details.left.text #"rall. "
  \startTextSpan 

% If you prefer the syntax \rit ... \stopRit:
stopRit = \stopTextSpan

\fixed c' {
  c4 d e \rit f |
  g1 \stopRit
  c4 d e _\rall f |
  g1 \stopTextSpan
}