doc: mention bigFileThreshold for packing

Knowing about the core.bigFileThreshold configuration variable is
helpful when examining pack file size differences between repositories.
Add a reference to it to the manpages a user is likely to read in this
situation.

Capitalize CONFIGURATION for consistency with other pages having such a
section.

Signed-off-by: Christian Walther <cwalther@gmx.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-pack-objects.txt

@@ -400,6 +400,17 @@ Note that we pick a single island for each regex to go into, using "last
 one wins" ordering (which allows repo-specific config to take precedence
 over user-wide config, and so forth).
 
+
+CONFIGURATION
+-------------
+
+Various configuration variables affect packing, see
+linkgit:git-config[1] (search for "pack" and "delta").
+
+Notably, delta compression is not used on objects larger than the
+`core.bigFileThreshold` configuration variable and on files with the
+attribute `delta` set to false.
+
 SEE ALSO
 --------
 linkgit:git-rev-list[1]

Documentation/git-repack.txt

@@ -165,9 +165,12 @@ depth is 4095.
 	Pass the `--delta-islands` option to `git-pack-objects`, see
 	linkgit:git-pack-objects[1].
 
-Configuration
+CONFIGURATION
 -------------
 
+Various configuration variables affect packing, see
+linkgit:git-config[1] (search for "pack" and "delta").
+
 By default, the command passes `--delta-base-offset` option to
 'git pack-objects'; this typically results in slightly smaller packs,
 but the generated packs are incompatible with versions of Git older than
@@ -178,6 +181,10 @@ need to set the configuration variable `repack.UseDeltaBaseOffset` to
 is unaffected by this option as the conversion is performed on the fly
 as needed in that case.
 
+Delta compression is not used on objects larger than the
+`core.bigFileThreshold` configuration variable and on files with the
+attribute `delta` set to false.
+
 SEE ALSO
 --------
 linkgit:git-pack-objects[1]