use Python to delete empty directories
move deletion past the usage help
upgrade ipython to version 2.1.0
Trac #16303: 'make doc-clean' calls system-wide 'git', which may break 'make distclean'

From sage-devel:
{{{
sage-6.2 build successfully, but perhaps the make doc-clean was not
successful

make doc-clean
cd src/doc && make -j4 clean
Deleting generated docs...
rm -rf en/reference/*/sage
rm -rf en/reference/*/sagenb
rm -rf en/reference/sage
rm -rf en/reference/sagenb
rm -rf output
git clean -f -d .
make[1]: git: No such file or directory
make[1]: *** [clean] Error 1
make: *** [doc-clean] Error 2

What am I supposed to do?
}}}

In `src/doc/Makefile` we have:
{{{
#!make
all:
        @echo "Please build the doc using either 'make doc' from
SAGE_ROOT, or"
        @echo "'sage -docbuild all html'. See 'sage -docbuild help' for
more informations."
clean:
        @echo "Deleting generated docs..."
        rm -rf en/reference/*/sage
        rm -rf en/reference/*/sagenb
        rm -rf en/reference/sage
        rm -rf en/reference/sagenb
        rm -rf output
        git clean -f -d .
}}}

and that's called from the top-level `Makefile` (outside a Sage
subshell).

URL: http://trac.sagemath.org/16303
Reported by: leif
Ticket author(s): Volker Braun
Reviewer(s): Anne Schilling, John Palmieri, Leif Leonhardy
Trac #16488: upgrade to IPython 2.1

Upstream tarball: https://github.com/ipython/ipython/releases/download/r
el-2.1.0/ipython-2.1.0.tar.gz

URL: http://trac.sagemath.org/16488
Reported by: was
Ticket author(s): R. Andrew Ohana
Reviewer(s): Thierry Monteil