[PATCH 7/7] rebase: implement --[no-]autostash and rebase.autostash

[Ramkumar Ramachandra <artagnon@gmail.com>]

This new feature allows a rebase to be executed on a dirty worktree or
index.  It works by creating a temporary "dangling merge commit" out
of the worktree and index changes (via 'git stash create'), and
automatically applying it after a successful rebase or abort.

rebase stores the SHA-1 hex of the temporary merge commit, along with
the rest of the rebase state, in either
.git/{rebase-merge,rebase-apply}/autostash depending on the kind of
rebase.  Since $state_dir is automatically removed at the end of a
successful rebase or abort, so is the autostash.

The advantage of this approach is that we do not affect the normal
stash's reflogs, making the autostash invisible to the end-user.  This
means that you can use 'git stash' during a rebase as usual.

When the autostash application results in a conflict, we push
$state_dir/autostash onto the normal stash and remove $state_dir
ending the rebase.  The user can inspect the stash, and pop or drop at
any time.

Most significantly, this feature means that a caller like pull (with
pull.rebase set to true) can easily be patched to remove the
require_clean_work_tree restriction.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
---
 Documentation/config.txt     |   8 +++
 Documentation/git-rebase.txt |  10 +++
 git-rebase.sh                |  43 ++++++++++++-
 t/t3420-rebase-autostash.sh  | 148 +++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 206 insertions(+), 3 deletions(-)
 create mode 100755 t/t3420-rebase-autostash.sh

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 6e53fc5..7fd4035 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -1867,6 +1867,14 @@ rebase.stat::
 rebase.autosquash::
 	If set to true enable '--autosquash' option by default.
 
+rebase.autostash::
+	When set to true, automatically create a temporary stash
+	before the operation begins, and apply it after the operation
+	ends.  This means that you can run rebase on a dirty worktree.
+	However, use with care: the final stash application after a
+	successful rebase might result in non-trivial conflicts.
+	Defaults to false.
+
 receive.autogc::
 	By default, git-receive-pack will run "git-gc --auto" after
 	receiving data from git-push and updating refs.  You can stop
diff --git a/Documentation/git-rebase.txt b/Documentation/git-rebase.txt
index aca8405..c84854a 100644
--- a/Documentation/git-rebase.txt
+++ b/Documentation/git-rebase.txt
@@ -208,6 +208,9 @@ rebase.stat::
 rebase.autosquash::
 	If set to true enable '--autosquash' option by default.
 
+rebase.autostash::
+	If set to true enable '--autostash' option by default.
+
 OPTIONS
 -------
 --onto <newbase>::
@@ -394,6 +397,13 @@ If the '--autosquash' option is enabled by default using the
 configuration variable `rebase.autosquash`, this option can be
 used to override and disable this setting.
 
+--[no-]autostash::
+	Automatically create a temporary stash before the operation
+	begins, and apply it after the operation ends.  This means
+	that you can run rebase on a dirty worktree.  However, use
+	with care: the final stash application after a successful
+	rebase might result in non-trivial conflicts.
+
 --no-ff::
 	With --interactive, cherry-pick all rebased commits instead of
 	fast-forwarding over the unchanged ones.  This ensures that the
diff --git a/git-rebase.sh b/git-rebase.sh
index f8b533d..709ef6b 100755
--- a/git-rebase.sh
+++ b/git-rebase.sh
@@ -13,6 +13,7 @@ git-rebase --continue | --abort | --skip | --edit-todo
  Available options are
 v,verbose!         display a diffstat of what changed upstream
 q,quiet!           be quiet. implies --no-stat
+autostash!         automatically stash/stash pop before and after
 onto=!             rebase onto given branch instead of upstream
 p,preserve-merges! try to recreate merges instead of ignoring them
 s,strategy=!       use the given merge strategy
@@ -64,6 +65,7 @@ apply_dir="$GIT_DIR"/rebase-apply
 verbose=
 diffstat=
 test "$(git config --bool rebase.stat)" = true && diffstat=t
+autostash="$(git config --bool rebase.autostash || echo false)"
 git_am_opt=
 rebase_root=
 force_rebase=
@@ -143,6 +145,28 @@ move_to_original_branch () {
 	esac
 }
 
+finish_rebase () {
+	if test -f "$state_dir/autostash"
+	then
+		stash_sha1=$(cat "$state_dir/autostash")
+		if git stash apply $stash_sha1 2>&1 >/dev/null
+		then
+			echo "Applied autostash"
+		else
+			ref_stash=refs/stash &&
+			: >>"$GIT_DIR/logs/$ref_stash" &&
+			git update-ref -m "autostash" $ref_stash $stash_sha1 \
+				|| die "$(eval_gettext 'Cannot store $stash_sha1')"
+			echo "
+$(gettext 'Applying autostash resulted in conflicts.
+Your changes are safe in the stash.
+You can apply or drop it at any time.')"
+		fi
+	fi
+	git gc --auto &&
+	rm -rf "$state_dir"
+}
+
 run_specific_rebase () {
 	if [ "$interactive_rebase" = implied ]; then
 		GIT_EDITOR=:
@@ -153,8 +177,7 @@ run_specific_rebase () {
 	ret=$?
 	if test $ret -eq 0
 	then
-		git gc --auto &&
-		rm -rf "$state_dir"
+		finish_rebase
 	fi
 	exit $ret
 }
@@ -248,6 +271,9 @@ do
 	--stat)
 		diffstat=t
 		;;
+	--autostash)
+		autostash=true
+		;;
 	-v)
 		verbose=t
 		diffstat=t
@@ -348,7 +374,7 @@ abort)
 		;;
 	esac
 	output git reset --hard $orig_head
-	rm -r "$state_dir"
+	finish_rebase
 	exit
 	;;
 edit-todo)
@@ -487,6 +513,17 @@ case "$#" in
 	;;
 esac
 
+if test "$autostash" = true && ! (require_clean_work_tree) 2>/dev/null
+then
+	stash_sha1=$(git stash create "autostash") \
+		|| die "$(gettext 'Cannot autostash')"
+	mkdir -p "$state_dir" &&
+	echo $stash_sha1 >"$state_dir/autostash" &&
+	stash_abbrev=$(git rev-parse --short $stash_sha1) &&
+	echo "$(eval_gettext 'Created autostash: $stash_abbrev')" &&
+	git reset --hard
+fi
+
 require_clean_work_tree "rebase" "$(gettext "Please commit or stash them.")"
 
 # Now we are rebasing commits $upstream..$orig_head (or with --root,
diff --git a/t/t3420-rebase-autostash.sh b/t/t3420-rebase-autostash.sh
new file mode 100755
index 0000000..479cbb2
--- /dev/null
+++ b/t/t3420-rebase-autostash.sh
@@ -0,0 +1,148 @@
+#!/bin/sh
+#
+# Copyright (c) 2013 Ramkumar Ramachandra
+#
+
+test_description='git rebase --autostash tests'
+. ./test-lib.sh
+
+test_expect_success setup '
+	echo hello-world >file0 &&
+	git add . &&
+	test_tick &&
+	git commit -m "initial commit" &&
+	git checkout -b feature-branch &&
+	echo another-hello >file1 &&
+	echo goodbye >file2 &&
+	git add . &&
+	test_tick &&
+	git commit -m "second commit" &&
+	echo final-goodbye >file3 &&
+	git add . &&
+	test_tick &&
+	git commit -m "third commit" &&
+	git checkout -b unrelated-onto-branch master &&
+	echo unrelated >file4 &&
+	git add . &&
+	test_tick &&
+	git commit -m "unrelated commit" &&
+	git checkout -b related-onto-branch master &&
+	echo conflicting-change >file2 &&
+	git add . &&
+	test_tick &&
+	git commit -m "related commit"
+'
+
+testrebase() {
+	type=$1
+	dotest=$2
+
+	test_expect_success "rebase$type: dirty worktree, non-conflicting rebase" '
+		test_config rebase.autostash true &&
+		git reset --hard &&
+		git checkout -b rebased-feature-branch feature-branch &&
+		test_when_finished git branch -D rebased-feature-branch &&
+		echo dirty >>file3 &&
+		git rebase$type unrelated-onto-branch &&
+		grep unrelated file4 &&
+		grep dirty file3 &&
+		git checkout feature-branch
+	'
+
+	test_expect_success "rebase$type: dirty index, non-conflicting rebase" '
+		test_config rebase.autostash true &&
+		git reset --hard &&
+		git checkout -b rebased-feature-branch feature-branch &&
+		test_when_finished git branch -D rebased-feature-branch &&
+		echo dirty >>file3 &&
+		git add file3 &&
+		git rebase$type unrelated-onto-branch &&
+		grep unrelated file4 &&
+		grep dirty file3 &&
+		git checkout feature-branch
+	'
+
+	test_expect_success "rebase$type: conflicting rebase" '
+		test_config rebase.autostash true &&
+		git reset --hard &&
+		git checkout -b rebased-feature-branch feature-branch &&
+		test_when_finished git branch -D rebased-feature-branch &&
+		echo dirty >>file3 &&
+		test_must_fail git rebase$type related-onto-branch &&
+		test_path_is_file $dotest/autostash &&
+		! grep dirty file3 &&
+		rm -rf $dotest &&
+		git reset --hard &&
+		git checkout feature-branch
+	'
+
+	test_expect_success "rebase$type: --continue" '
+		test_config rebase.autostash true &&
+		git reset --hard &&
+		git checkout -b rebased-feature-branch feature-branch &&
+		test_when_finished git branch -D rebased-feature-branch &&
+		echo dirty >>file3 &&
+		test_must_fail git rebase$type related-onto-branch &&
+		test_path_is_file $dotest/autostash &&
+		! grep dirty file3 &&
+		echo "conflicting-plus-goodbye" >file2 &&
+		git add file2 &&
+		git rebase --continue &&
+		test_path_is_missing $dotest/autostash &&
+		grep dirty file3 &&
+		git checkout feature-branch
+	'
+
+	test_expect_success "rebase$type: --skip" '
+		test_config rebase.autostash true &&
+		git reset --hard &&
+		git checkout -b rebased-feature-branch feature-branch &&
+		test_when_finished git branch -D rebased-feature-branch &&
+		echo dirty >>file3 &&
+		test_must_fail git rebase$type related-onto-branch &&
+		test_path_is_file $dotest/autostash &&
+		! grep dirty file3 &&
+		git rebase --skip &&
+		test_path_is_missing $dotest/autostash &&
+		grep dirty file3 &&
+		git checkout feature-branch
+	'
+
+	test_expect_success "rebase$type: --abort" '
+		test_config rebase.autostash true &&
+		git reset --hard &&
+		git checkout -b rebased-feature-branch feature-branch &&
+		test_when_finished git branch -D rebased-feature-branch &&
+		echo dirty >>file3 &&
+		test_must_fail git rebase$type related-onto-branch &&
+		test_path_is_file $dotest/autostash &&
+		! grep dirty file3 &&
+		git rebase --abort &&
+		test_path_is_missing $dotest/autostash &&
+		grep dirty file3 &&
+		git checkout feature-branch
+	'
+
+	test_expect_success "rebase$type: non-conflicting rebase, conflicting stash" '
+		test_config rebase.autostash true &&
+		git reset --hard &&
+		git checkout -b rebased-feature-branch feature-branch &&
+		test_when_finished git branch -D rebased-feature-branch &&
+		echo dirty >file4 &&
+		git add file4 &&
+		git rebase$type unrelated-onto-branch &&
+		test_path_is_missing $dotest &&
+		git reset --hard &&
+		grep unrelated file4 &&
+		! grep dirty file4 &&
+		git checkout feature-branch &&
+		git stash pop &&
+		grep dirty file4
+	'
+}
+
+testrebase "" .git/rebase-apply
+testrebase " --merge" .git/rebase-merge
+testrebase " --interactive" .git/rebase-merge
+
+test_done
-- 
1.8.3.rc1.51.gd7a04de