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, 67 insertions, 0 deletions

diff --git a/third_party/git/t/t6401-merge-criss-cross.sh b/third_party/git/t/t6401-merge-criss-cross.sh
new file mode 100755
index 000000000000..9d5e992878fa
--- /dev/null
+++ b/third_party/git/t/t6401-merge-criss-cross.sh
@@ -0,0 +1,67 @@
+#!/bin/sh
+#
+# Copyright (c) 2005 Fredrik Kuivinen
+#
+
+# See https://lore.kernel.org/git/Pine.LNX.4.44.0504271254120.4678-100000@wax.eds.org/ for a
+# nice description of what this is about.
+
+
+test_description='Test criss-cross merge'
+. ./test-lib.sh
+
+test_expect_success 'prepare repository' '
+	test_write_lines 1 2 3 4 5 6 7 8 9 >file &&
+	git add file &&
+	git commit -m "Initial commit" file &&
+
+	git branch A &&
+	git branch B &&
+	git checkout A &&
+
+	test_write_lines 1 2 3 4 5 6 7 "8 changed in B8, branch A" 9 >file &&
+	git commit -m "B8" file &&
+	git checkout B &&
+
+	test_write_lines 1 2 "3 changed in C3, branch B" 4 5 6 7 8 9 >file &&
+	git commit -m "C3" file &&
+	git branch C3 &&
+
+	git merge -m "pre E3 merge" A &&
+
+	test_write_lines 1 2 "3 changed in E3, branch B. New file size" 4 5 6 7 "8 changed in B8, branch A" 9 >file &&
+	git commit -m "E3" file &&
+
+	git checkout A &&
+	git merge -m "pre D8 merge" C3 &&
+	test_write_lines 1 2 "3 changed in C3, branch B" 4 5 6 7 "8 changed in D8, branch A. New file size 2" 9 >file &&
+
+	git commit -m D8 file
+'
+
+test_expect_success 'Criss-cross merge' '
+	git merge -m "final merge" B
+'
+
+test_expect_success 'Criss-cross merge result' '
+	cat <<-\EOF >file-expect &&
+	1
+	2
+	3 changed in E3, branch B. New file size
+	4
+	5
+	6
+	7
+	8 changed in D8, branch A. New file size 2
+	9
+	EOF
+
+	test_cmp file-expect file
+'
+
+test_expect_success 'Criss-cross merge fails (-s resolve)' '
+	git reset --hard A^ &&
+	test_must_fail git merge -s resolve -m "final merge" B
+'
+
+test_done