The function rewrite_one is used to rewrite a single
parent of the current commit, and is used by rewrite_parents
to rewrite all the parents.
Decouple the dependence between them by making rewrite_one
a callback function that is passed to rewrite_parents. Then
export rewrite_parents for reuse by the line history browser.
We will use this function in line-log.c.
Signed-off-by: Bo Yang <struggleyb.nku@gmail.com> Signed-off-by: Thomas Rast <trast@student.ethz.ch> Signed-off-by: Junio C Hamano <gitster@pobox.com>