The U-Boot download script does its work from the repository root
instead going into the newly created dirs, unlike the coreboot
counterpart. It should run the board-specific extra.sh files with the
downloaded paths as their working directory. Do so by a subshell.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>

The no-argument form of the U-Boot download script prepare trees for all
boards when run with no arguments, like the corresponding script for
coreboot. The usage text for this case was removed without any changes
to the corresponding code, assume it was by mistake and add it back.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>

Removing the git dirs was part of deblobbing, which Libreboot no longer
cares about. The variable that triggers it is no more. Remove the dead
code.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>

osboot is now part of libreboot, and will soon shut down.
libreboot now conforms to osboot policy.

Downloading coreboot and U-Boot takes quite the disk space and bandwith.
We don't need to download entire repos, only the revisions that we are
interested in.

Use the --depth=1 option to only download the files we need. Since the
initial clones may not have our target revision, always try to fetch it.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>

Keeping the git repositories is useful while development, e.g. to avoid
git cloning repositories over and over again while debugging download
scripts. Setting the NODELETE environment variable keeps the blobs and
the git repositories. Allow a slightly finer-tuned version of this where
we can keep only the git-related files by setting the variable to "git".

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>

The coreboot download removes .git folders as they still contain the
removed blobs, remove those in the U-Boot version as well.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>

Although it's unlikely, boards might want to run extra commands after
the board-specific U-Boot directories are prepared. Copy the existing
mechanism for that from the coreboot download script to the U-Boot one.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>

Boards may need different sets of patches to be applied to their U-Boot
builds, copy the existing mechanism from the coreboot download script to
the U-Boot download script.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>

The coreboot download script tries to update submodules, since coreboot
does use git submodules to retrieve and compile the projects it depends
on. Although U-Boot doesn't use submodules, try to update them anyway to
match the coreboot download script.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>