Programmatically managing VCS

I have the following issue: a script periodically (once a day, for instance) pulls rarely-changing mostly-textual data from various sources.  I wish to keep a history of the state before each script run.  It certainly sounds like a job for VCS control system.

I remember someone here praising Mercurial as the best VCS ever.  Does it have a fairly stable and reliable command-line interface such that (given enough information) it will not interactively prompt the user (which is a non-interactive script)?

I never used Mercurial, but at work we use Perforce (more than 500 programmers) which is now free (20 users/workspaces max). It has great UI and CLI tools, as well as API/SDKs for most programming languages.