git-repack: repo.usedeltabaseoffset

When configuration variable `repack.UseDeltaBaseOffset` is set
for the repository, 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 (and including) v1.4.3.

We will make it default to true sometime in the future, but not
for a while.

Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/config.txt

@@ -224,6 +224,10 @@ pull.octopus::
 pull.twohead::
 	The default merge strategy to use when pulling a single branch.
 
+repack.usedeltabaseoffset::
+	Allow gitlink:git-repack[1] to create packs that uses
+	delta-base offset.  Defaults to false.
+
 show.difftree::
 	The default gitlink:git-diff-tree[1] arguments to be used
 	for gitlink:git-show[1].

Documentation/git-repack.txt

@@ -66,6 +66,20 @@ OPTIONS
 	to be applied that many times to get to the necessary object.
 
 
+Configuration
+-------------
+
+When configuration variable `repack.UseDeltaBaseOffset` is set
+for the repository, 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 (and including) v1.4.3; do not set
+the variable in a repository that older version of git needs to
+be able to read (this includes repositories from which packs can
+be copied out over http or rsync, and people who obtained packs
+that way can try to use older git with it).
+
+
 Author
 ------
 Written by Linus Torvalds <torvalds@osdl.org>

git-repack.sh

@@ -3,7 +3,7 @@
 # Copyright (c) 2005 Linus Torvalds
 #
 
-USAGE='[-a] [-d] [-f] [-l] [-n] [-q]'
+USAGE='[-a] [-d] [-f] [-l] [-n] [-q] [--window=N] [--depth=N]'
 . git-sh-setup
 
 no_update_info= all_into_one= remove_redundant=
@@ -24,6 +24,15 @@ do
 	shift
 done
 
+# Later we will default repack.UseDeltaBaseOffset to true
+default_dbo=false
+
+case "`git repo-config --bool repack.usedeltabaseoffset ||
+       echo $default_dbo`" in
+true)
+	extra="$extra --delta-base-offset" ;;
+esac
+
 PACKDIR="$GIT_OBJECT_DIRECTORY/pack"
 PACKTMP="$GIT_DIR/.tmp-$$-pack"
 rm -f "$PACKTMP"-*