In a similar fashion as in previous commits, move the function
`write_filtered_pack()` out of the builtin and into its own compilation
unit.
This function is now part of the repack.h API, but implemented in its
own "repack-filtered.c" unit as it is a separate component from other
kinds of repacking operations.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Taylor Blau