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, 120 insertions, 0 deletions

diff --git a/third_party/git/t/t6012-rev-list-simplify.sh b/third_party/git/t/t6012-rev-list-simplify.sh
index a10f0df02b..7fc10f8593 100755
--- a/third_party/git/t/t6012-rev-list-simplify.sh
+++ b/third_party/git/t/t6012-rev-list-simplify.sh
@@ -154,4 +154,124 @@ test_expect_success '--full-diff is not affected by --parents' '
 	test_cmp expected actual
 '
 
+#
+# Create a new history to demonstrate the value of --show-pulls
+# with respect to the subtleties of simplified history, --full-history,
+# and --simplify-merges.
+#
+#   .-A---M-----C--N---O---P
+#  /     / \  \  \/   /   /
+# I     B   \  R-'`-Z'   /
+#  \   /     \/         /
+#   \ /      /\        /
+#    `---X--'  `---Y--'
+#
+# This example is explained in Documentation/rev-list-options.txt
+
+test_expect_success 'rebuild repo' '
+	rm -rf .git * &&
+	git init &&
+	git switch -c topic &&
+
+	echo base >file &&
+	git add file &&
+	test_commit I &&
+
+	echo A >file &&
+	git add file &&
+	test_commit A &&
+
+	git switch -c branchB I &&
+	echo B >file &&
+	git add file &&
+	test_commit B &&
+
+	git switch topic &&
+	test_must_fail git merge -m "M" B &&
+	echo A >file &&
+	echo B >>file &&
+	git add file &&
+	git merge --continue &&
+	note M &&
+
+	echo C >other &&
+	git add other &&
+	test_commit C &&
+
+	git switch -c branchX I &&
+	echo X >file &&
+	git add file &&
+	test_commit X &&
+
+	git switch -c branchR M &&
+	git merge -m R -Xtheirs X &&
+	note R &&
+
+	git switch topic &&
+	git merge -m N R &&
+	note N &&
+
+	git switch -c branchY M &&
+	echo Y >y &&
+	git add y &&
+	test_commit Y &&
+
+	git switch -c branchZ C &&
+	echo Z >z &&
+	git add z &&
+	test_commit Z &&
+
+	git switch topic &&
+	git merge -m O Z &&
+	note O &&
+
+	git merge -m P Y &&
+	note P
+'
+
+check_result 'X I' -- file
+check_result 'N R X I' --show-pulls -- file
+
+check_result 'P O N R X M B A I' --full-history --topo-order -- file
+check_result 'N R X M B A I' --simplify-merges --topo-order --show-pulls -- file
+check_result 'R X M B A I' --simplify-merges --topo-order -- file
+check_result 'N M A I' --first-parent -- file
+check_result 'N M A I' --first-parent --show-pulls -- file
+
+# --ancestry-path implies --full-history
+check_result 'P O N R M' --topo-order \
+	--ancestry-path A..HEAD -- file
+check_result 'P O N R M' --topo-order \
+	--show-pulls \
+	--ancestry-path A..HEAD -- file
+check_result 'P O N R M' --topo-order \
+	--full-history \
+	--ancestry-path A..HEAD -- file
+check_result 'R M' --topo-order \
+	--simplify-merges \
+	--ancestry-path A..HEAD -- file
+check_result 'N R M' --topo-order \
+	--simplify-merges --show-pulls \
+	--ancestry-path A..HEAD -- file
+
+test_expect_success 'log --graph --simplify-merges --show-pulls' '
+	cat >expect <<-\EOF &&
+	* N
+	*   R
+	|\  
+	| * X
+	* |   M
+	|\ \  
+	| * | B
+	| |/  
+	* / A
+	|/  
+	* I
+	EOF
+	git log --graph --pretty="%s" \
+		--simplify-merges --show-pulls \
+		-- file >actual &&
+	test_cmp expect actual
+'
+
 test_done