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, 131 insertions, 0 deletions

diff --git a/third_party/git/t/t6404-recursive-merge.sh b/third_party/git/t/t6404-recursive-merge.sh
new file mode 100755
index 000000000000..332cfc53fd88
--- /dev/null
+++ b/third_party/git/t/t6404-recursive-merge.sh
@@ -0,0 +1,131 @@
+#!/bin/sh
+
+test_description='Test merge without common ancestors'
+. ./test-lib.sh
+
+# This scenario is based on a real-world repository of Shawn Pearce.
+
+# 1 - A - D - F
+#   \   X   /
+#     B   X
+#       X   \
+# 2 - C - E - G
+
+GIT_COMMITTER_DATE="2006-12-12 23:28:00 +0100"
+export GIT_COMMITTER_DATE
+
+test_expect_success 'setup tests' '
+	echo 1 >a1 &&
+	git add a1 &&
+	GIT_AUTHOR_DATE="2006-12-12 23:00:00" git commit -m 1 a1 &&
+
+	git checkout -b A master &&
+	echo A >a1 &&
+	GIT_AUTHOR_DATE="2006-12-12 23:00:01" git commit -m A a1 &&
+
+	git checkout -b B master &&
+	echo B >a1 &&
+	GIT_AUTHOR_DATE="2006-12-12 23:00:02" git commit -m B a1 &&
+
+	git checkout -b D A &&
+	git rev-parse B >.git/MERGE_HEAD &&
+	echo D >a1 &&
+	git update-index a1 &&
+	GIT_AUTHOR_DATE="2006-12-12 23:00:03" git commit -m D &&
+
+	git symbolic-ref HEAD refs/heads/other &&
+	echo 2 >a1 &&
+	GIT_AUTHOR_DATE="2006-12-12 23:00:04" git commit -m 2 a1 &&
+
+	git checkout -b C &&
+	echo C >a1 &&
+	GIT_AUTHOR_DATE="2006-12-12 23:00:05" git commit -m C a1 &&
+
+	git checkout -b E C &&
+	git rev-parse B >.git/MERGE_HEAD &&
+	echo E >a1 &&
+	git update-index a1 &&
+	GIT_AUTHOR_DATE="2006-12-12 23:00:06" git commit -m E &&
+
+	git checkout -b G E &&
+	git rev-parse A >.git/MERGE_HEAD &&
+	echo G >a1 &&
+	git update-index a1 &&
+	GIT_AUTHOR_DATE="2006-12-12 23:00:07" git commit -m G &&
+
+	git checkout -b F D &&
+	git rev-parse C >.git/MERGE_HEAD &&
+	echo F >a1 &&
+	git update-index a1 &&
+	GIT_AUTHOR_DATE="2006-12-12 23:00:08" git commit -m F &&
+
+	test_oid_cache <<-EOF
+	idxstage1 sha1:ec3fe2a791706733f2d8fa7ad45d9a9672031f5e
+	idxstage1 sha256:b3c8488929903aaebdeb22270cb6d36e5b8724b01ae0d4da24632f158c99676f
+	EOF
+'
+
+test_expect_success 'combined merge conflicts' '
+	test_must_fail env GIT_TEST_COMMIT_GRAPH=0 git merge -m final G
+'
+
+test_expect_success 'result contains a conflict' '
+	cat >expect <<-\EOF &&
+	<<<<<<< HEAD
+	F
+	=======
+	G
+	>>>>>>> G
+	EOF
+
+	test_cmp expect a1
+'
+
+test_expect_success 'virtual trees were processed' '
+	git ls-files --stage >out &&
+
+	cat >expect <<-EOF &&
+	100644 $(test_oid idxstage1) 1	a1
+	100644 $(git rev-parse F:a1) 2	a1
+	100644 $(git rev-parse G:a1) 3	a1
+	EOF
+
+	test_cmp expect out
+'
+
+test_expect_success 'refuse to merge binary files' '
+	git reset --hard &&
+	printf "\0" >binary-file &&
+	git add binary-file &&
+	git commit -m binary &&
+	git checkout G &&
+	printf "\0\0" >binary-file &&
+	git add binary-file &&
+	git commit -m binary2 &&
+	test_must_fail git merge F >merge.out 2>merge.err &&
+	grep "Cannot merge binary files: binary-file (HEAD vs. F)" merge.err
+'
+
+test_expect_success 'mark rename/delete as unmerged' '
+
+	git reset --hard &&
+	git checkout -b delete &&
+	git rm a1 &&
+	test_tick &&
+	git commit -m delete &&
+	git checkout -b rename HEAD^ &&
+	git mv a1 a2 &&
+	test_tick &&
+	git commit -m rename &&
+	test_must_fail git merge delete &&
+	test 1 = $(git ls-files --unmerged | wc -l) &&
+	git rev-parse --verify :2:a2 &&
+	test_must_fail git rev-parse --verify :3:a2 &&
+	git checkout -f delete &&
+	test_must_fail git merge rename &&
+	test 1 = $(git ls-files --unmerged | wc -l) &&
+	test_must_fail git rev-parse --verify :2:a2 &&
+	git rev-parse --verify :3:a2
+'
+
+test_done