Builds a Larry Wall format patch(1) file between two
releases, that can be fed directly into the
program to bring an old release up-to-date with the new
release. (This is one of the few CVS commands that
operates directly from the repository, and doesn't
require a prior checkout.) The diff output is sent to
the standard output device.
You can specify (using the standard `-r' and `-D' options) any combination of one or two revisions or dates. If only one revision or date is specified, the patch file reflects differences between that revision or date and the current head revisions in the RCS file.
Note that if the software release affected is contained
in more than one directory, then it may be necessary to
specify the `-p' option to the
patch command when
patching the old sources, so that
patch is able to find
the files that are located in other directories.