git-checkout-index, flag ordering and --prefix kludgy handling

I already knew that git-checkout-cache -a -f is wrong. But I didn't know that 

git-checkout-index -a --prefix=/home/paolo/Uml/space.mnt/paolo/Linux-2.6.git/

is. It checks out the files in the cwd, then parses --prefix and does nothing there, as no name is specified.

Also, the SYNOPSIS of the man page is rather misleading:

git-checkout-index [-u] [-q] [-a] [-f] [-n] [--prefix=<string>] [--] <file>...

seems to suggest that prefix can go after -f, how it's reasonable to do.

At least, this should be documented in the man page; but I think that fixing this (via two getopt() invocations rather than one, the first for flags like --prefix and the rest for actions) is probably a better thing to do.

Actually, given the audience, saying that "-a" and "filename" are both actions (which are executed when seen on the command line) would be a better explaination - and a reference to the "find" command (which behaves similarly) would be worth.

However, find *does* accept "options" (like -maxdepth) in any cmd line place.