Re: [PATCH] fast-import: Increase the default pack depth to 50

From: Jeff King <peff@peff.net>
Date: Jun 8, 2017, 07:05 UTC
Message-ID: <20170608070537.zgrcxhl57u4akzvq@sigill.intra.peff.net>
In-Reply-To: <20170608053436.9121-1-mh@glandium.org>

On Thu, Jun 08, 2017 at 02:34:36PM +0900, Mike Hommey wrote:

Show 11 quoted lines

> In 618e613a70, 10 years ago, the default for pack depth used for
> git-pack-objects and git-repack was changed from 10 to 50, while
> leaving fast-import's default to 10.
> 
> There doesn't seem to be a reason besides oversight for the change not
> having happened in fast-import as well.
> 
> Interestingly, fast-import uses pack.depth when it's set, and the
> git-config manual says the default for pack.depth is 50. While the
> git-fast-import manual does say the default depth is 10, the
> inconsistency is also confusing.

Makes sense. If anything, fast-import would want to allow a deeper depth than normal, since (IIRC) its delta chains are always completely linear. Whereas in a real pack, if we decide not to make a delta off the 50th item in a chain, we usually find the 48th or 49th, and end up with a bushier graph.

It probably doesn't matter that much, though, as you'd really want to `repack -f` afterwards if you care about getting good deltas. And one base object every 50 versions is probably fine for keeping the initial pack manageable.

> ---
>  Documentation/git-fast-import.txt | 2 +-
>  fast-import.c                     | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)

Patch itself looks obviously correct.

-Peff