Subversion was a little trickier. Assuming you've installed Subversion or have it already, install SvnX. Start the application once and it will put the svnx shell script into your ~/bin/svnx. Assuming you don't have ~/bin/ on path, you can add the following to your ~/bash_profile:
After restarting Terminal.app, browse to a checked-out subversion repository and just type the following to see a log:
alias svnx='~/bin/svnx wc . && ~/bin/svnx log .'
Mercurial is a little tricky, but mostly because the tool I use is called Murky, not hgx, as you might think. Hgx is easier to remember, that is what I call my alias. Assuming you've installed subversion or have it already, install Murky. Then, add the following to your ~/bash_profile:
After restarting Terminal.app, browse to a checked-out Mercurial repository and type the following to see its log:
alias hgx='open -a Murky .'
(Thanks to Jens Alfke for the Mercurial command-line solution.)