[oe] [PATCH] Make git more usable

[Yann Dirson]

This series allows to install the essential functionnality of git
while still consuming as less space as possible.  Space-consuming
binaries are split to separate ipk's.

The final patch activates installation of gitk - it is only partially
working, but does not force build of anything that's not built in the
default shr image, and can hopefully bring someone into looking at
what seems to be an issue in tcl/tk packaging.