Several sites we need to clone our dependencies from (eg. freedesktop.org)
have pretty unreliable servers, so our CI jobs often fail just because
of temporary clone failure.
Therefore adding a separate cloning script, which is more clever with automatic
retries, but it also tries to keep the traffic low (eg. trying shallow clones
if possible) and automatically detecting whether we're pulling a ref or a
direct commit.
Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
