Re: git filter-branch should run git gc --auto

[Junio C Hamano <gitster@pobox.com>]

Mike Hommey <mh@glandium.org> writes:

> I wonder if it wouldn't be possible to have filter-branch use
> fast-import, so that it would create a pack instead of a lot of loose
> objects.

I do not think it will help.  The objects in packs fast-import
creates cannot be accessed from outside fast-import.  Not even
the rest of the core routines running inside that fast-import
process cannot access them via the usual read_sha1_file()
interface, as described in detail in a recent thread [*1*].  The
only way to make it available while you are still feeding new
data to fast-import is to explicitly tell it to finalize the
current pack by issuing a 'mark' command (and fast-import will
start writing to a new pack).

And filters need to be able to read the objects previous steps
produced to do their work.

Which means that instead of having to deal with many loose
objects, you will now face many little packs, each contains data
changed perhaps at most one commit's worth.  You would need to
"repack -a -d" to consolidate these little packs every once in a
while, and I suspect more often than you would need to repack
loose objects, as handling many packs is much more expensive
than handling many loose objects.

[Reference]

*1* http://thread.gmane.org/gmane.comp.version-control.git/70964/focus=71076