cvs.csh man page
cvs.sh — C shell log-in script for CVS users
The cvs.csh script is sourced when a user of a C log-in shell is logged in. The purpose is to set CVS_RSH environment variable, so that a cvs user connecting to a remote CVS server utilizes SSH-secured connection by default.
if ( "$?CVS_RSH" == 0 ) setenv CVS_RSH ssh
csh(1), cvs(1), bash(1).