merge(3p/git): Merge git subtree at v2.29.2 r/1890

This also bumps the stable nixpkgs to 20.09 as of 2020-11-21, because
there is some breakage in the git build related to the netrc
credentials helper which someone has taken care of in nixpkgs.

The stable channel is not used for anything other than git, so this
should be fine.

Change-Id: I3575a19dab09e1e9556cf8231d717de9890484fb

1 files changed, 170 insertions, 0 deletions

diff --git a/third_party/git/t/t3424-rebase-empty.sh b/third_party/git/t/t3424-rebase-empty.sh
new file mode 100755
index 000000000000..5e1045a0afc9
--- /dev/null
+++ b/third_party/git/t/t3424-rebase-empty.sh
@@ -0,0 +1,170 @@
+#!/bin/sh
+
+test_description='git rebase of commits that start or become empty'
+
+. ./test-lib.sh
+
+test_expect_success 'setup test repository' '
+	test_write_lines 1 2 3 4 5 6 7 8 9 10 >numbers &&
+	test_write_lines A B C D E F G H I J >letters &&
+	git add numbers letters &&
+	git commit -m A &&
+
+	git branch upstream &&
+	git branch localmods &&
+
+	git checkout upstream &&
+	test_write_lines A B C D E >letters &&
+	git add letters &&
+	git commit -m B &&
+
+	test_write_lines 1 2 3 4 five 6 7 8 9 ten >numbers &&
+	git add numbers &&
+	git commit -m C &&
+
+	git checkout localmods &&
+	test_write_lines 1 2 3 4 five 6 7 8 9 10 >numbers &&
+	git add numbers &&
+	git commit -m C2 &&
+
+	git commit --allow-empty -m D &&
+
+	test_write_lines A B C D E >letters &&
+	git add letters &&
+	git commit -m "Five letters ought to be enough for anybody"
+'
+
+test_expect_failure 'rebase (apply-backend)' '
+	test_when_finished "git rebase --abort" &&
+	git checkout -B testing localmods &&
+	# rebase (--apply) should not drop commits that start empty
+	git rebase --apply upstream &&
+
+	test_write_lines D C B A >expect &&
+	git log --format=%s >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'rebase --merge --empty=drop' '
+	git checkout -B testing localmods &&
+	git rebase --merge --empty=drop upstream &&
+
+	test_write_lines D C B A >expect &&
+	git log --format=%s >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'rebase --merge uses default of --empty=drop' '
+	git checkout -B testing localmods &&
+	git rebase --merge upstream &&
+
+	test_write_lines D C B A >expect &&
+	git log --format=%s >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'rebase --merge --empty=keep' '
+	git checkout -B testing localmods &&
+	git rebase --merge --empty=keep upstream &&
+
+	test_write_lines D C2 C B A >expect &&
+	git log --format=%s >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'rebase --merge --empty=ask' '
+	git checkout -B testing localmods &&
+	test_must_fail git rebase --merge --empty=ask upstream &&
+
+	git rebase --skip &&
+
+	test_write_lines D C B A >expect &&
+	git log --format=%s >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'rebase --interactive --empty=drop' '
+	git checkout -B testing localmods &&
+	git rebase --interactive --empty=drop upstream &&
+
+	test_write_lines D C B A >expect &&
+	git log --format=%s >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'rebase --interactive --empty=keep' '
+	git checkout -B testing localmods &&
+	git rebase --interactive --empty=keep upstream &&
+
+	test_write_lines D C2 C B A >expect &&
+	git log --format=%s >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'rebase --interactive --empty=ask' '
+	git checkout -B testing localmods &&
+	test_must_fail git rebase --interactive --empty=ask upstream &&
+
+	git rebase --skip &&
+
+	test_write_lines D C B A >expect &&
+	git log --format=%s >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'rebase --interactive uses default of --empty=ask' '
+	git checkout -B testing localmods &&
+	test_must_fail git rebase --interactive upstream &&
+
+	git rebase --skip &&
+
+	test_write_lines D C B A >expect &&
+	git log --format=%s >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'rebase --merge --empty=drop --keep-empty' '
+	git checkout -B testing localmods &&
+	git rebase --merge --empty=drop --keep-empty upstream &&
+
+	test_write_lines D C B A >expect &&
+	git log --format=%s >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'rebase --merge --empty=drop --no-keep-empty' '
+	git checkout -B testing localmods &&
+	git rebase --merge --empty=drop --no-keep-empty upstream &&
+
+	test_write_lines C B A >expect &&
+	git log --format=%s >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'rebase --merge --empty=keep --keep-empty' '
+	git checkout -B testing localmods &&
+	git rebase --merge --empty=keep --keep-empty upstream &&
+
+	test_write_lines D C2 C B A >expect &&
+	git log --format=%s >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'rebase --merge --empty=keep --no-keep-empty' '
+	git checkout -B testing localmods &&
+	git rebase --merge --empty=keep --no-keep-empty upstream &&
+
+	test_write_lines C2 C B A >expect &&
+	git log --format=%s >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'rebase --merge does not leave state laying around' '
+	git checkout -B testing localmods~2 &&
+	git rebase --merge upstream &&
+
+	test_path_is_missing .git/CHERRY_PICK_HEAD &&
+	test_path_is_missing .git/MERGE_MSG
+'
+
+test_done