init_skiplist() took a file consisting of SHA-1s and comments and added
the objects to an oidset. This functionality is useful for other
commands and will be moved to oidset.c in a future commit.
In preparation for that move, this commit renames it to
oidset_parse_file() to reflect its more generic usage and cleans up a
few of the names.
Signed-off-by: Barret Rhoden <brho@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>