[PATCH] document delta attribute

I always wanted a way to turn off delta compression. Turns out git had one,
but it wasn't documented. Added documentation based on
the commit message of a74db82e15cd8a2c53a4a83e9a36dc7bf7a4c750.

Skipped the .jpg example though because I don't want to over-encourage use
of the attribute. (Also because jpeg file changes might delta-compress
well, if only metadata is changed.)

Signed-off-by: Joey Hess <redacted>
---
 Documentation/gitattributes.txt |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)

diff --git a/Documentation/gitattributes.txt b/Documentation/gitattributes.txt
index 1195e83..e3e3d2c 100644
--- a/Documentation/gitattributes.txt
+++ b/Documentation/gitattributes.txt

@@ -577,6 +577,18 @@ If this attribute is not set or has an invalid value, the value of the
 (See linkgit:git-config[1]).
 
 
+Packing objects
+~~~~~~~~~~~~~~~
+
+`delta`
+^^^^^^^
+
+This attribute controls whether linkgit:git-pack-objects[1] will try
+to delta compress files. The attribute is set by default. You may benefit
+from unsetting it for certain large binary files for which attempting delta
+compression will only use CPU cycles and memory.
+
+
 USING ATTRIBUTE MACROS
 ----------------------
 

-- 
1.6.4.3