You do not remember modifying driver.c, so you want to see what has happened to that file.
$ cd tc $ cvs diff driver.c
This command runs
diff to compare the version of driver.c
that you checked out with your working copy. When you see the output
you remember that you added a command line option that enabled the
optimization pass. You check it in, and release the module.
$ cvs commit -m "Added an optimization pass" driver.c Checking in driver.c; /usr/local/cvsroot/tc/driver.c,v <-- driver.c new revision: 1.2; previous revision: 1.1 done $ cd .. $ cvs release -d tc ? tc You have  altered files in this repository. Are you sure you want to release (and delete) directory `tc': y