Re: [PATCH 4/8] git-repack --max-pack-size: add fixup_header_footer()

Nicolas Pitre [off-list ref] wrote:

I'd be really tempted to create a pack v4 which only change is to still 
have the pack header at the beginning of the pack like we do today, but 
include the header in the pack SHA1 computation at the end of the stream 
only.  This way the pack SHA1 could be computed as the pack is 
generated, and the header fixed up without having to read the entire 
pack back.  I think it was Geert Bosch who proposed this and it makes 
tons of sense IMHO.

Yes.  If we really are heading in this direction of needing to
correct object counts, we should make that change.  Its trivial
to hang onto that header for the duration of the rest of the data
processing, and tack it onto the end for final SHA-1 computation.

Since pack v4 looks like it will be a dev cycle longer than these
index format changes and pack-splitting changes, I have to say I
agree with you.  Lets move "pack v4" back to "pack v5" and make v4
just a shift of where the header is included in the SHA-1.

We're heading where I said I didn't want to go, which is two
file format changes in 2007.  But I think that ship has already
sailed...  Folks need support for larger repositories now, and pack
v4/v5 (whatever you call our dictionary work) just isn't ready.
Nor does it solve the big packfile problems that this current work
is addressing.

-- 
Shawn.