Re: [PATCH v3 7/9] pack-objects: introduce pack.allowPackReuse

From: Jeff King <peff@peff.net>
Date: Dec 9, 2019, 07:14 UTC
Message-ID: <20191209071412.GG40570@coredump.intra.peff.net>
In-Reply-To: <20191115141541.11149-8-chriscool@tuxfamily.org>

On Fri, Nov 15, 2019 at 03:15:39PM +0100, Christian Couder wrote:

> From: Jeff King <peff@peff.net>
> 
> Let's make it possible to configure if we want pack reuse or not.

...because? :)

I mostly used it for debugging and performance testing. I don't think there should be any big downside to using it that would cause people to want to turn it off. But it _might_ cause larger packs, because we wouldn't consider the reused objects as bases for finding new deltas.

I think the documentation could mention this. And maybe make it a bit more clear what "reuse" means.

So maybe:

diff --git a/Documentation/config/pack.txt b/Documentation/config/pack.txt
index 58323a351f..0dac580581 100644
--- a/Documentation/config/pack.txt
+++ b/Documentation/config/pack.txt
@@ -28,8 +28,11 @@ all existing objects. You can force recompression by passing the -F option
 to linkgit:git-repack[1].
 
 pack.allowPackReuse::
-	When true, which is the default, Git will try to reuse parts
-	of existing packfiles when preparing new packfiles.
+	When true, and when reachability bitmaps are enabled,
+	pack-objects will try to send parts of the bitmapped packfile
+	verbatim. This can reduce memory and CPU usage to serve fetches,
+	but might result in sending a slightly larger pack. Defaults to
+	true.
 
 pack.island::
 	An extended regular expression configuring a set of delta

-Peff