get_remote_url(): use the same data source as ls-remote to get remote urls

get_remote_url(): use the same data source as ls-remote to get remote urls

The formerly implemented algorithm behaved differently to
remote.c:remote_get() at least for remotes that contain a slash.  While the
former just assumes a/b is a path the latter checks the config for
remote."a/b" first which is more reasonable.

This removes the last user of git-parse-remote.sh:get_data_source(), so
this function is removed.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>