12. Keyword substitution
As long as you edit source files inside a working
directory you can always find out the state of
your files via `cvs status' and `cvs log'.
But as soon as you export the files from your
development environment it becomes harder to identify
which revisions they are.
CVS can use a mechanism known as keyword
substitution (or keyword expansion) to help
identifying the files. Embedded strings of the form
$keyword:…$ in a file are replaced
with strings of the form
$keyword:value$ whenever you obtain
a new revision of the file.