tar old options

tar has an old options style where the arguments are listed after the switches:
tar cvzf foo.tar.gz foo
or even
tar fxv foo.tar

So if there's only one argument, the order of the switches doesn't matter. This is in contrast to the short and long options style.

But this can be confusing since:
tar cvfz foo.tar.gz foo
is different from
tar -cvfz foo.tar.gz foo

See the info page for more details about the old option style.

Git's data model

Git has the most amazingly simple data model which makes it easy to have a decent understanding of how the tool works instead of just assuming that it does some magic behind the scenes. Of course, with this simple model, some of the most complex interactions take place.

As a point, Git became self-hosting in about two days of coding yet it took Subversion 14 months before it was self-hosting.