From 6cb5728c43f34a7348e128b44b80d00b9417cb19 Mon Sep 17 00:00:00 2001
From: Chris Packham <judge.packham@gmail.com>
Date: Wed, 3 Jul 2013 21:02:02 +1200
Subject: submodule update: allow custom command to update submodule working
 tree

Users can set submodule.$name.update to '!command' which will cause
'command' to be run instead of checkout/merge/rebase. This allows
the user finer-grained control over how the update is done.

The primary motivation for this was interoperability with stgit;
however being able to intercept the submodule update process may
prove useful for integrating with or extending other tools.

Signed-off-by: Chris Packham <judge.packham@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/git-submodule.txt |  4 +++-
 git-submodule.sh                |  6 ++++++
 t/t7406-submodule-update.sh     | 29 +++++++++++++++++++++++++++++
 3 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/Documentation/git-submodule.txt b/Documentation/git-submodule.txt
index e5767134b1..2f18f7daf8 100644
--- a/Documentation/git-submodule.txt
+++ b/Documentation/git-submodule.txt
@@ -159,7 +159,9 @@ update::
 	This will make the submodules HEAD be detached unless `--rebase` or
 	`--merge` is specified or the key `submodule.$name.update` is set to
 	`rebase`, `merge` or `none`. `none` can be overridden by specifying
-	`--checkout`.
+	`--checkout`. Setting the key `submodule.$name.update` to `!command`
+	will cause `command` to be run. `command` can be any arbitrary shell
+	command that takes a single argument, namely the sha1 to update to.
 +
 If the submodule is not yet initialized, and you just want to use the
 setting as stored in .gitmodules, you can automatically initialize the
diff --git a/git-submodule.sh b/git-submodule.sh
index 945e296d30..c87515de10 100755
--- a/git-submodule.sh
+++ b/git-submodule.sh
@@ -860,6 +860,12 @@ Maybe you want to use 'update --init'?")"
 				say_msg="$(eval_gettext "Submodule path '\$displaypath': merged in '\$sha1'")"
 				must_die_on_failure=yes
 				;;
+			!*)
+				command="${update_module#!}"
+				die_msg="$(eval_gettext "Execution of '\$command \$sha1' failed in submodule  path '\$prefix\$sm_path'")"
+				say_msg="$(eval_gettext "Submodule path '\$prefix\$sm_path': '\$command \$sha1'")"
+				must_die_on_failure=yes
+				;;
 			*)
 				command="git checkout $subforce -q"
 				die_msg="$(eval_gettext "Unable to checkout '\$sha1' in submodule path '\$displaypath'")"
diff --git a/t/t7406-submodule-update.sh b/t/t7406-submodule-update.sh
index cdb0538392..bc7cfcd835 100755
--- a/t/t7406-submodule-update.sh
+++ b/t/t7406-submodule-update.sh
@@ -294,6 +294,35 @@ test_expect_success 'submodule update - checkout in .git/config' '
 	)
 '
 
+test_expect_success 'submodule update - command in .git/config' '
+	(cd super &&
+	 git config submodule.submodule.update "!git checkout"
+	) &&
+	(cd super/submodule &&
+	  git reset --hard HEAD^
+	) &&
+	(cd super &&
+	 (cd submodule &&
+	  compare_head
+	 ) &&
+	 git submodule update submodule &&
+	 cd submodule &&
+	 ! compare_head
+	)
+'
+
+test_expect_success 'submodule update - command in .git/config catches failure' '
+	(cd super &&
+	 git config submodule.submodule.update "!false"
+	) &&
+	(cd super/submodule &&
+	  git reset --hard HEAD^
+	) &&
+	(cd super &&
+	 test_must_fail git submodule update submodule
+	)
+'
+
 test_expect_success 'submodule init picks up rebase' '
 	(cd super &&
 	 git config -f .gitmodules submodule.rebasing.update rebase &&
-- 
cgit v1.2.3