Typing svn log spits out an incredibly long, useless list on a command line. I have no idea why that is the default. If I wanted to read (or even could read) 30
svn log
To add to what others have said, you could also create an alias in your .bashrc or .bash_aliases file:
alias svnlog='svn log -l 30 | less'
or whatever you want as your default