From a21e6adf900332ff6a98f4f9293901cfb6185df5 Mon Sep 17 00:00:00 2001
From: "Kyle J. McKay" <mackyle@gmail.com>
Date: Sun, 18 Jun 2017 11:07:46 -0700
Subject: [PATCH] config: prefer core.compression=5

When initializing a new repository or updating a repository's
config, prefer to set a core.compression value of 5 (leaving an
existing valid but different value alone on config update).

There are two reasons for this:

1) If left unset the defaults for core.compression and
   core.looseCompression differ.  That implies potentially
   wasteful recompression may take place when packing loose
   objects into packs.

2) The default value (-1) which specifies the zlib default
   (which is currently 6) does not provide the best tradeoff.

Number (1) could be corrected simply by setting a core.compression
value of -1 which would provide a core.looseCompression default
and levels would then match and (1) would go away.

However, it turns out that the speed difference between levels 4
and 5 is generally somewhat less than the speed difference between
levels 5 and 6 (the zlib default) while the space savings between
levels 4 and 5 is generally double the space savings between
levels 5 and 6.

This may not be the case generally but seems to be the case when
dealing with Git objects.  In other words, level 5 is the
inflection point of the graph, not 6.  Thus level 5 provides the
better speed, space and time tradeoff than level 6 does.

Make it so.

Signed-off-by: Kyle J. McKay <mackyle@gmail.com>
---
 Girocco/Project.pm           |  2 ++
 jailsetup.sh                 |  1 +
 toolbox/update-all-config.sh | 13 +++++++++++++
 3 files changed, 16 insertions(+)

diff --git a/Girocco/Project.pm b/Girocco/Project.pm
index eaa5de9..13f8c3c 100644
--- a/Girocco/Project.pm
+++ b/Girocco/Project.pm
@@ -883,6 +883,8 @@ sub _setup {
 	}
 	# hooks never world writable
 	chmod 02775, $self->{path}."/hooks" or die "chmod 02775 $self->{path}/hooks failed: $!";
+	system($Girocco::Config::git_bin, '--git-dir='.$self->{path}, 'config', 'core.compression', '5') == 0
+		or die "setting core.compression failed: $?";
 	system($Girocco::Config::git_bin, '--git-dir='.$self->{path}, 'config', 'core.logAllRefUpdates', 'false') == 0
 		or die "disabling core.logAllRefUpdates failed: $?";
 	system($Girocco::Config::git_bin, '--git-dir='.$self->{path}, 'config', 'core.ignoreCase', 'false') == 0
diff --git a/jailsetup.sh b/jailsetup.sh
index 3e7387c..0c1a726 100755
--- a/jailsetup.sh
+++ b/jailsetup.sh
@@ -177,6 +177,7 @@ if [ -n "$cfg_jgit_compatible_bitmaps" ]; then
 else
 	update_config_item pack.writeBitmapHashCache true 1
 fi
+update_config_item core.compression 5
 update_config_item http.lowSpeedLimit 1
 update_config_item http.lowSpeedTime 600
 update_config_item receive.maxInputSize "${cfg_max_receive_size:-0}" 1
diff --git a/toolbox/update-all-config.sh b/toolbox/update-all-config.sh
index 5a8bf5a..4a185d9 100755
--- a/toolbox/update-all-config.sh
+++ b/toolbox/update-all-config.sh
@@ -279,6 +279,19 @@ eval "$cmd" | \
 		[ -z "$bad" ] || continue
 		[ -n "$dryrun" ] || change_fperm config
 		readconfiglist
+		cmplvl="$(configitem core.compression || :)"
+		case "$cmplvl" in
+			"5"|"")
+				;;
+			"-1"|"0"|"1"|"2"|"3"|"4"|"6"|"7"|"8"|"9")
+				pmsg "WARNING: suboptimal core.compression value left unchanged: \"$cmplvl\""
+				;;
+			*)
+				pmsg "WARNING: replacing invalid core.compression value"
+				cmplvl=
+				;;
+		esac
+		[ -n "$cmplvl" ] || do_config core.compression 5
 		grpshr="$(configitem core.sharedrepository || :)"
 		if [ -z "$grpshr" ] || isboolfalse "$grpshr"; then
 			do_config core.sharedrepository 1
-- 
2.11.4.GIT