cvs-update-filter is a compiled Lisp function in `pcvs.el'.

(cvs-update-filter PROC STRING)

Filter function for PCL-CVS.
This function gets the output that CVS sends to stdout. It inserts
the STRING into (process-buffer PROC) but it also checks if CVS is waiting
for a lock file. If so, it inserts a message cookie in the *cvs* buffer.