Merge branch 'ph/submodule-rebase' (early part)

* 'ph/submodule-rebase' (early part):
  Rename submodule.<name>.rebase to submodule.<name>.update
  git-submodule: add support for --rebase.

Conflicts:
	Documentation/git-submodule.txt
	git-submodule.sh

4 files changed, 192 insertions, 6 deletions

diff --git a/Documentation/git-submodule.txt b/Documentation/git-submodule.txt
index 14256c695b..cd8e861ce4 100644
--- a/Documentation/git-submodule.txt
+++ b/Documentation/git-submodule.txt
@@ -13,7 +13,7 @@ SYNOPSIS
 	      [--reference <repository>] [--] <repository> <path>
 'git submodule' [--quiet] status [--cached] [--] [<path>...]
 'git submodule' [--quiet] init [--] [<path>...]
-'git submodule' [--quiet] update [--init] [-N|--no-fetch]
+'git submodule' [--quiet] update [--init] [-N|--no-fetch] [--rebase]
 	      [--reference <repository>] [--] [<path>...]
 'git submodule' [--quiet] summary [--summary-limit <n>] [commit] [--] [<path>...]
 'git submodule' [--quiet] foreach <command>
@@ -115,7 +115,8 @@ init::
 update::
 	Update the registered submodules, i.e. clone missing submodules and
 	checkout the commit specified in the index of the containing repository.
-	This will make the submodules HEAD be detached.
+	This will make the submodules HEAD be detached unless '--rebase' is
+	specified or the key `submodule.$name.update` is set to	`rebase`.
 +
 If the submodule is not yet initialized, and you just want to use the
 setting as stored in .gitmodules, you can automatically initialize the
@@ -179,6 +180,15 @@ OPTIONS
 	This option is only valid for the update command.
 	Don't fetch new objects from the remote site.
 
+--rebase::
+	This option is only valid for the update command.
+	Rebase the current branch onto the commit recorded in the
+	superproject. If this option is given, the submodule's HEAD will not
+	be detached. If a a merge failure prevents this process, you will have
+	to resolve these failures with linkgit:git-rebase[1].
+	If the key `submodule.$name.update` is set to `rebase`, this option is
+	implicit.
+
 --reference <repository>::
 	This option is only valid for add and update commands.  These
 	commands sometimes need to clone a remote repository. In this case,
diff --git a/Documentation/gitmodules.txt b/Documentation/gitmodules.txt
index d1a17e2625..1b67f0a9f1 100644
--- a/Documentation/gitmodules.txt
+++ b/Documentation/gitmodules.txt
@@ -30,6 +30,15 @@ submodule.<name>.path::
 submodule.<name>.url::
 	Defines an url from where the submodule repository can be cloned.
 
+submodule.<name>.update::
+	Defines what to do when the submodule is updated by the superproject.
+	If 'checkout' (the default), the new commit specified in the
+	superproject will be checked out in the submodule on a detached HEAD.
+	If 'rebase', the current branch of the submodule will be rebased onto
+	the commit specified in the superproject.
+	This config option is overridden if 'git submodule update' is given
+	the '--rebase' option.
+
 
 EXAMPLES
 --------
diff --git a/git-submodule.sh b/git-submodule.sh
index ab1ed02a66..19a3a840fd 100755
--- a/git-submodule.sh
+++ b/git-submodule.sh
@@ -18,6 +18,7 @@ quiet=
 reference=
 cached=
 nofetch=
+update=
 
 #
 # print stuff on stdout unless -q was specified
@@ -310,6 +311,11 @@ cmd_init()
 		git config submodule."$name".url "$url" ||
 		die "Failed to register url for submodule path '$path'"
 
+		upd="$(git config -f .gitmodules submodule."$name".update)"
+		test -z "$upd" ||
+		git config submodule."$name".update "$upd" ||
+		die "Failed to register update mode for submodule path '$path'"
+
 		say "Submodule '$name' ($url) registered for path '$path'"
 	done
 }
@@ -337,6 +343,10 @@ cmd_update()
 			shift
 			nofetch=1
 			;;
+		-r|--rebase)
+			shift
+			update="rebase"
+			;;
 		--reference)
 			case "$2" in '') usage ;; esac
 			reference="--reference=$2"
@@ -369,6 +379,7 @@ cmd_update()
 	do
 		name=$(module_name "$path") || exit
 		url=$(git config submodule."$name".url)
+		update_module=$(git config submodule."$name".update)
 		if test -z "$url"
 		then
 			# Only mention uninitialized submodules when its
@@ -389,6 +400,11 @@ cmd_update()
 			die "Unable to find current revision in submodule path '$path'"
 		fi
 
+		if ! test -z "$update"
+		then
+			update_module=$update
+		fi
+
 		if test "$subsha1" != "$sha1"
 		then
 			force=
@@ -404,11 +420,22 @@ cmd_update()
 				die "Unable to fetch in submodule path '$path'"
 			fi
 
-			(unset GIT_DIR; cd "$path" &&
-				  git-checkout $force -q "$sha1") ||
-			die "Unable to checkout '$sha1' in submodule path '$path'"
+			case "$update_module" in
+			rebase)
+				command="git rebase"
+				action="rebase"
+				msg="rebased onto"
+				;;
+			*)
+				command="git checkout $force -q"
+				action="checkout"
+				msg="checked out"
+				;;
+			esac
 
-			say "Submodule path '$path': checked out '$sha1'"
+			(unset GIT_DIR; cd "$path" && $command "$sha1") ||
+			die "Unable to $action '$sha1' in submodule path '$path'"
+			say "Submodule path '$path': $msg '$sha1'"
 		fi
 	done
 }
diff --git a/t/t7406-submodule-update.sh b/t/t7406-submodule-update.sh
new file mode 100755
index 0000000000..0773fe405b
--- /dev/null
+++ b/t/t7406-submodule-update.sh
@@ -0,0 +1,140 @@
+#!/bin/sh
+#
+# Copyright (c) 2009 Red Hat, Inc.
+#
+
+test_description='Test updating submodules
+
+This test verifies that "git submodule update" detaches the HEAD of the
+submodule and "git submodule update --rebase" does not detach the HEAD.
+'
+
+. ./test-lib.sh
+
+
+compare_head()
+{
+    sha_master=`git-rev-list --max-count=1 master`
+    sha_head=`git-rev-list --max-count=1 HEAD`
+
+    test "$sha_master" = "$sha_head"
+}
+
+
+test_expect_success 'setup a submodule tree' '
+	echo file > file &&
+	git add file &&
+	test_tick &&
+	git commit -m upstream
+	git clone . super &&
+	git clone super submodule &&
+	(cd super &&
+	 git submodule add ../submodule submodule &&
+	 test_tick &&
+	 git commit -m "submodule" &&
+	 git submodule init submodule
+	) &&
+	(cd submodule &&
+	echo "line2" > file &&
+	git add file &&
+	git commit -m "Commit 2"
+	) &&
+	(cd super &&
+	 (cd submodule &&
+	  git pull --rebase origin
+	 ) &&
+	 git add submodule &&
+	 git commit -m "submodule update"
+	)
+'
+
+test_expect_success 'submodule update detaching the HEAD ' '
+	(cd super/submodule &&
+	 git reset --hard HEAD~1
+	) &&
+	(cd super &&
+	 (cd submodule &&
+	  compare_head
+	 ) &&
+	 git submodule update submodule &&
+	 cd submodule &&
+	 ! compare_head
+	)
+'
+
+test_expect_success 'submodule update --rebase staying on master' '
+	(cd super/submodule &&
+	  git checkout master
+	) &&
+	(cd super &&
+	 (cd submodule &&
+	  compare_head
+	 ) &&
+	 git submodule update --rebase submodule &&
+	 cd submodule &&
+	 compare_head
+	)
+'
+
+test_expect_success 'submodule update - rebase in .git/config' '
+	(cd super &&
+	 git config submodule.submodule.update rebase
+	) &&
+	(cd super/submodule &&
+	  git reset --hard HEAD~1
+	) &&
+	(cd super &&
+	 (cd submodule &&
+	  compare_head
+	 ) &&
+	 git submodule update submodule &&
+	 cd submodule &&
+	 compare_head
+	)
+'
+
+test_expect_success 'submodule update - checkout in .git/config but --rebase given' '
+	(cd super &&
+	 git config submodule.submodule.update checkout
+	) &&
+	(cd super/submodule &&
+	  git reset --hard HEAD~1
+	) &&
+	(cd super &&
+	 (cd submodule &&
+	  compare_head
+	 ) &&
+	 git submodule update --rebase submodule &&
+	 cd submodule &&
+	 compare_head
+	)
+'
+
+test_expect_success 'submodule update - checkout in .git/config' '
+	(cd super &&
+	 git config submodule.submodule.update 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 init picks up rebase' '
+	(cd super &&
+	 git config submodule.rebasing.url git://non-existing/git &&
+	 git config submodule.rebasing.path does-not-matter &&
+	 git config submodule.rebasing.update rebase &&
+	 git submodule init rebasing &&
+	 test "rebase" = $(git config submodule.rebasing.update)
+	)
+'
+
+test_done