gitpkgv: Fix $GITPKV for a single named git source
Recipes that fetch from a single git source, assign a name to this
source and do not set SRCREV_FORMAT to this name will always get
a GITPKGV value of "default", which causes version-going-backwards QA
errors.
Fix this by automatically determining a suitable SRCREV_FORMAT from the
SRC_URI if none is set explicitly. This code does not run for multiple
git sources, because bitbake's fetcher enforces setting SRCREV_FORMAT
when multiple version-controlled sources are used.
Signed-off-by: Clemens Lang <clemens.lang@bmw-carit.de>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>