kernel-yocto: improve error checking on non-git repos
While non-git kernel repos are not the preferred format for a kernel upstream,
they are supported. Depending on the creator of the archive the expanded
source directory name varies. If the recipe for the kernel doesn't properly
set S to the right value, a cryptic git error message is produced. We can
detect the situation and offer some advice on how to fix the issue.
A second check is also added in this commit for archive based kernel repos
which won't have a SRCREV to validate. If we have no SRCREV or SRCREV is
INVALID, we can exit the branch validation step immediately. This saves yet
another cryptic git error message and simplifies a custom tgz based recipe.
Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
