[Buildroot] SCM management

[Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>]

Hi,

	During my work on barebox and the kernel
	I modify Buildroot to get the source from my git or the mainline
	and found out that we remove the tree everytime and re-clone it

	This is time consuming specialy in develeopment when you add new
	commit for other user which need to re-checkout your tree.

	So I'd like to propose a new way to manage the trees
	we could do something like on gentoo

	as example with git
	we clone a bare tre and store it in dl and do not remove it so if you
	need a new version of the tree you just need to fetch it and do not
	clone it again

	For this purpose I would propose to manage the tree like this in dl
	for git as example
	builddir/fetch/git-src/${package}

	for bzr
	builddir/fetch/bzr-src/${package}

	and to simplify the scm I would like to propose the manage it not via
	makefile rules but via scripts

Best Regards,
J.