Merge branch 'cw/rebase-i-root'

"git rebase [-i] --root $tip" can now be used to rewrite all the
history down to the root.

* cw/rebase-i-root:
  t3404: make test 57 work with dash and others
  Add tests for rebase -i --root without --onto
  rebase -i: support --root without --onto

Documentation/git-rebase.txt

@@ -10,7 +10,7 @@ SYNOPSIS
 [verse]
 'git rebase' [-i | --interactive] [options] [--exec <cmd>] [--onto <newbase>]
 	[<upstream>] [<branch>]
-'git rebase' [-i | --interactive] [options] [--exec <cmd>] --onto <newbase>
+'git rebase' [-i | --interactive] [options] [--exec <cmd>] [--onto <newbase>]
 	--root [<branch>]
 'git rebase' --continue | --skip | --abort
 
@@ -369,10 +369,11 @@ squash/fixup series.
 --root::
 	Rebase all commits reachable from <branch>, instead of
 	limiting them with an <upstream>.  This allows you to rebase
-	the root commit(s) on a branch.  Must be used with --onto, and
+	the root commit(s) on a branch.  When used with --onto, it
 	will skip changes already contained in <newbase> (instead of
-	<upstream>).  When used together with --preserve-merges, 'all'
-	root commits will be rewritten to have <newbase> as parent
+	<upstream>) whereas without --onto it will operate on every change.
+	When used together with both --onto and --preserve-merges,
+	'all' root commits will be rewritten to have <newbase> as parent
 	instead.
 
 --autosquash::

git-rebase--interactive.sh

@@ -415,6 +415,29 @@ record_in_rewritten() {
 	esac
 }
 
+do_pick () {
+	if test "$(git rev-parse HEAD)" = "$squash_onto"
+	then
+		# Set the correct commit message and author info on the
+		# sentinel root before cherry-picking the original changes
+		# without committing (-n).  Finally, update the sentinel again
+		# to include these changes.  If the cherry-pick results in a
+		# conflict, this means our behaviour is similar to a standard
+		# failed cherry-pick during rebase, with a dirty index to
+		# resolve before manually running git commit --amend then git
+		# rebase --continue.
+		git commit --allow-empty --allow-empty-message --amend \
+			   --no-post-rewrite -n -q -C $1 &&
+			pick_one -n $1 &&
+			git commit --allow-empty --allow-empty-message \
+				   --amend --no-post-rewrite -n -q -C $1 ||
+			die_with_patch $1 "Could not apply $1... $2"
+	else
+		pick_one $1 ||
+			die_with_patch $1 "Could not apply $1... $2"
+	fi
+}
+
 do_next () {
 	rm -f "$msg" "$author_script" "$amend" || exit
 	read -r command sha1 rest < "$todo"
@@ -426,16 +449,14 @@ do_next () {
 		comment_for_reflog pick
 
 		mark_action_done
-		pick_one $sha1 ||
-			die_with_patch $sha1 "Could not apply $sha1... $rest"
+		do_pick $sha1 "$rest"
 		record_in_rewritten $sha1
 		;;
 	reword|r)
 		comment_for_reflog reword
 
 		mark_action_done
-		pick_one $sha1 ||
-			die_with_patch $sha1 "Could not apply $sha1... $rest"
+		do_pick $sha1 "$rest"
 		git commit --amend --no-post-rewrite || {
 			warn "Could not amend commit after successfully picking $sha1... $rest"
 			warn "This is most likely due to an empty commit message, or the pre-commit hook"
@@ -449,8 +470,7 @@ do_next () {
 		comment_for_reflog edit
 
 		mark_action_done
-		pick_one $sha1 ||
-			die_with_patch $sha1 "Could not apply $sha1... $rest"
+		do_pick $sha1 "$rest"
 		warn "Stopped at $sha1... $rest"
 		exit_with_patch $sha1 0
 		;;

git-rebase.sh

@@ -32,7 +32,7 @@ SUBDIRECTORY_OK=Yes
 OPTIONS_KEEPDASHDASH=
 OPTIONS_SPEC="\
 git rebase [-i] [options] [--exec <cmd>] [--onto <newbase>] [<upstream>] [<branch>]
-git rebase [-i] [options] [--exec <cmd>] --onto <newbase> --root [<branch>]
+git rebase [-i] [options] [--exec <cmd>] [--onto <newbase>] --root [<branch>]
 git-rebase [-i] --continue | --abort | --skip
 --
  Available options are
@@ -378,6 +378,11 @@ and run me again.  I am stopping in case you still have something
 valuable there.'
 fi
 
+if test -n "$rebase_root" && test -z "$onto"
+then
+	test -z "$interactive_rebase" && interactive_rebase=implied
+fi
+
 if test -n "$interactive_rebase"
 then
 	type=interactive
@@ -411,7 +416,12 @@ then
 	die "invalid upstream $upstream_name"
 	upstream_arg="$upstream_name"
 else
-	test -z "$onto" && die "You must specify --onto when using --root"
+	if test -z "$onto"
+	then
+		empty_tree=`git hash-object -t tree /dev/null`
+		onto=`git commit-tree $empty_tree </dev/null`
+		squash_onto="$onto"
+	fi
 	unset upstream_name
 	unset upstream
 	test $# -gt 1 && usage

t/t3404-rebase-interactive.sh

@@ -872,4 +872,35 @@ test_expect_success 'rebase -i --exec without <CMD>' '
 	git checkout master
 '
 
+test_expect_success 'rebase -i --root re-order and drop commits' '
+	git checkout E &&
+	FAKE_LINES="3 1 2 5" git rebase -i --root &&
+	test E = $(git cat-file commit HEAD | sed -ne \$p) &&
+	test B = $(git cat-file commit HEAD^ | sed -ne \$p) &&
+	test A = $(git cat-file commit HEAD^^ | sed -ne \$p) &&
+	test C = $(git cat-file commit HEAD^^^ | sed -ne \$p) &&
+	test 0 = $(git cat-file commit HEAD^^^ | grep -c ^parent\ )
+'
+
+test_expect_success 'rebase -i --root retain root commit author and message' '
+	git checkout A &&
+	echo B >file7 &&
+	git add file7 &&
+	GIT_AUTHOR_NAME="Twerp Snog" git commit -m "different author" &&
+	FAKE_LINES="2" git rebase -i --root &&
+	git cat-file commit HEAD | grep -q "^author Twerp Snog" &&
+	git cat-file commit HEAD | grep -q "^different author$"
+'
+
+test_expect_success 'rebase -i --root temporary sentinel commit' '
+	git checkout B &&
+	(
+		FAKE_LINES="2" &&
+		export FAKE_LINES &&
+		test_must_fail git rebase -i --root
+	) &&
+	git cat-file commit HEAD | grep "^tree 4b825dc642cb" &&
+	git rebase --abort
+'
+
 test_done

t/t3412-rebase-root.sh

@@ -22,11 +22,6 @@ test_expect_success 'prepare repository' '
 	test_commit 4 B
 '
 
-test_expect_success 'rebase --root expects --onto' '
-	git checkout -B fail other &&
-	test_must_fail git rebase --root
-'
-
 test_expect_success 'rebase --root fails with too many args' '
 	git checkout -B fail other &&
 	test_must_fail git rebase --onto master --root fail fail