Signed-off-by: Andre McCurdy <armccurdy@gmail.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>

This class lets you use BBCLASSEXTEND to add a variant of the recipe that
fetches from an alternative URI (such as git:) instead of a tarball.

For example:

 BBCLASSEXTEND = "devupstream:target"
 SRC_URI_class-devupstream = "git://git.example.com/example"
 SRCREV_class-devupstream = "abcd1234"

This variant will have DEFAULT_PREFERENCE set to -1 so it needs to be selected
to be used, and any development-specific tweaks can be done with the
class-devupstream override, for example:

 DEPENDS_append_class-devupstream = " gperf-native"

 do_configure_prepend_class-devupstream() {
    touch ${S}/README
 }

It currently only supports creating a development variant of the target recipe,
not native or nativesdk.  The BBCLASSEXTEND syntax (devupstream:target) was
chosen so that support for native and nativesdk can be added at a later date.

Support for other version control systems such as subversion is limited, as
bitbake's automatic fetch dependencies on for example subversion-native are not
generated.

[ YOCTO #10215 ]

Signed-off-by: Ross Burton <ross.burton@intel.com>