init-upstream-tracking: tab->4space whitespace update

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
init-upstream-tracking: error reporting enhancements

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
OUT/Repo: add API to initialize tracking branch; use in scripts/init-upstream-tracking

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>