Checking out older versions of the code

It is sometimes necessary to check out older versions of a piece of code. Assume we wish to check out an old version of detci. If this is the case, the following steps will do this:

1. cd $PSI3/src/bin/detci
2. cvs update -D"2 months ago"

This will check the main repository and provide you with the code as it stood exactly 2 months ago. CVS is quite impressive in this respect: It will accept all sorts of input to the -D option. You could even use -D"a fortnight ago" and CVS would get the correct version. (But it doesn't get "two fortnights ago" right.) You can always get the recent version back by simply using -D"now" or -A. Note that subsequent updates of the current code will use the same date you give with the -D option. (See the CVS documentation about so-called ``sticky tags''.)