[jc: the original from Pavel was limiting the variable names to only
fetch and url, but I loosened it to take valid variable names.]
[jc: cherry-picked from 'master', since people seem to be reinventing
this many times.]
Signed-off-by: Pavel Roskin <proski@gnu.org> Signed-off-by: Junio C Hamano <junkio@cox.net>