rebase -i: learn to rebase root commit

Teach git-rebase -i a new option --root, which instructs it to rebase
the entire history leading up to <branch>.  This is mainly for
symmetry with ordinary git-rebase; it cannot be used to edit the root
commit in-place (it requires --onto <newbase>).  Commits that already
exist in <newbase> are skipped.

In the normal mode of operation, this is fairly straightforward.  We
run cherry-pick in a loop, and cherry-pick has supported picking the
root commit since f95ebf7 (Allow cherry-picking root commits,
2008-07-04).

In --preserve-merges mode, we track the mapping from old to rewritten
commits and use it to update the parent list of each commit.  In this
case, we define 'rebase -i -p --root --onto $onto $branch' to rewrite
the parent list of all root commit(s) on $branch to contain $onto
instead.

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 101 insertions, 0 deletions

diff --git a/t/t3412-rebase-root.sh b/t/t3412-rebase-root.sh
index dd919100d6..6359580262 100755
--- a/t/t3412-rebase-root.sh
+++ b/t/t3412-rebase-root.sh
@@ -67,6 +67,100 @@ test_expect_success 'pre-rebase got correct input (2)' '
 	test "z$(cat .git/PRE-REBASE-INPUT)" = z--root,work2
 '
 
+test_expect_success 'rebase -i --root --onto <newbase>' '
+	git checkout -b work3 other &&
+	GIT_EDITOR=: git rebase -i --root --onto master &&
+	git log --pretty=tformat:"%s" > rebased3 &&
+	test_cmp expect rebased3
+'
+
+test_expect_success 'pre-rebase got correct input (3)' '
+	test "z$(cat .git/PRE-REBASE-INPUT)" = z--root,
+'
+
+test_expect_success 'rebase -i --root --onto <newbase> <branch>' '
+	git branch work4 other &&
+	GIT_EDITOR=: git rebase -i --root --onto master work4 &&
+	git log --pretty=tformat:"%s" > rebased4 &&
+	test_cmp expect rebased4
+'
+
+test_expect_success 'pre-rebase got correct input (4)' '
+	test "z$(cat .git/PRE-REBASE-INPUT)" = z--root,work4
+'
+
+test_expect_success 'rebase -i -p with linear history' '
+	git checkout -b work5 other &&
+	GIT_EDITOR=: git rebase -i -p --root --onto master &&
+	git log --pretty=tformat:"%s" > rebased5 &&
+	test_cmp expect rebased5
+'
+
+test_expect_success 'pre-rebase got correct input (5)' '
+	test "z$(cat .git/PRE-REBASE-INPUT)" = z--root,
+'
+
+test_expect_success 'set up merge history' '
+	git checkout other^ &&
+	git checkout -b side &&
+	echo 5 > C &&
+	git add C &&
+	git commit -m 5 &&
+	git checkout other &&
+	git merge side
+'
+
+sed 's/#/ /g' > expect-side <<'EOF'
+*   Merge branch 'side' into other
+|\##
+| * 5
+* | 4
+|/##
+* 3
+* 2
+* 1
+EOF
+
+test_expect_success 'rebase -i -p with merge' '
+	git checkout -b work6 other &&
+	GIT_EDITOR=: git rebase -i -p --root --onto master &&
+	git log --graph --topo-order --pretty=tformat:"%s" > rebased6 &&
+	test_cmp expect-side rebased6
+'
+
+test_expect_success 'set up second root and merge' '
+	git symbolic-ref HEAD refs/heads/third &&
+	rm .git/index &&
+	rm A B C &&
+	echo 6 > D &&
+	git add D &&
+	git commit -m 6 &&
+	git checkout other &&
+	git merge third
+'
+
+sed 's/#/ /g' > expect-third <<'EOF'
+*   Merge branch 'third' into other
+|\##
+| * 6
+* |   Merge branch 'side' into other
+|\ \##
+| * | 5
+* | | 4
+|/ /##
+* | 3
+|/##
+* 2
+* 1
+EOF
+
+test_expect_success 'rebase -i -p with two roots' '
+	git checkout -b work7 other &&
+	GIT_EDITOR=: git rebase -i -p --root --onto master &&
+	git log --graph --topo-order --pretty=tformat:"%s" > rebased7 &&
+	test_cmp expect-third rebased7
+'
+
 test_expect_success 'setup pre-rebase hook that fails' '
 	mkdir -p .git/hooks &&
 	cat >.git/hooks/pre-rebase <<EOF &&
@@ -83,4 +177,11 @@ test_expect_success 'pre-rebase hook stops rebase' '
 	test 0 = $(git rev-list other...stops1 | wc -l)
 '
 
+test_expect_success 'pre-rebase hook stops rebase -i' '
+	git checkout -b stops2 other &&
+	GIT_EDITOR=: test_must_fail git rebase --root --onto master &&
+	test "z$(git symbolic-ref HEAD)" = zrefs/heads/stops2
+	test 0 = $(git rev-list other...stops2 | wc -l)
+'
+
 test_done