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, 95 insertions, 0 deletions

diff --git a/third_party/git/t/t6431-merge-criscross.sh b/third_party/git/t/t6431-merge-criscross.sh
new file mode 100755
index 000000000000..3824756a02ec
--- /dev/null
+++ b/third_party/git/t/t6431-merge-criscross.sh
@@ -0,0 +1,95 @@
+#!/bin/sh
+
+test_description='merge-recursive backend test'
+
+. ./test-lib.sh
+
+#         A      <- create some files
+#        / \
+#       B   C    <- cause rename/delete conflicts between B and C
+#      /     \
+#     |\     /|
+#     | D   E |
+#     |  \ /  |
+#     |   X   |
+#     |  / \  |
+#     | /   \ |
+#     |/     \|
+#     F       G  <- merge E into B, D into C
+#      \     /
+#       \   /
+#        \ /
+#         H      <- recursive merge crashes
+#
+
+# initialize
+test_expect_success 'setup repo with criss-cross history' '
+	mkdir data &&
+
+	# create a bunch of files
+	n=1 &&
+	while test $n -le 10
+	do
+		echo $n > data/$n &&
+		n=$(($n+1)) ||
+		return 1
+	done &&
+
+	# check them in
+	git add data &&
+	git commit -m A &&
+	git branch A &&
+
+	# a file in one branch
+	git checkout -b B A &&
+	git rm data/9 &&
+	git add data &&
+	git commit -m B &&
+
+	# with a branch off of it
+	git branch D &&
+
+	# put some commits on D
+	git checkout D &&
+	echo testD > data/testD &&
+	git add data &&
+	git commit -m D &&
+
+	# back up to the top, create another branch and cause
+	# a rename conflict with the file we deleted earlier
+	git checkout -b C A &&
+	git mv data/9 data/new-9 &&
+	git add data &&
+	git commit -m C &&
+
+	# with a branch off of it
+	git branch E &&
+
+	# put a commit on E
+	git checkout E &&
+	echo testE > data/testE &&
+	git add data &&
+	git commit -m E &&
+
+	# now, merge E into B
+	git checkout B &&
+	test_must_fail git merge E &&
+	# force-resolve
+	git add data &&
+	git commit -m F &&
+	git branch F &&
+
+	# and merge D into C
+	git checkout C &&
+	test_must_fail git merge D &&
+	# force-resolve
+	git add data &&
+	git commit -m G &&
+	git branch G
+'
+
+test_expect_success 'recursive merge between F and G does not cause segfault' '
+	git merge F
+'
+
+test_done