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

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

third_party/git/t/t7810-grep.sh

@@ -72,6 +72,11 @@ test_expect_success setup '
 	# Still a no-op.
 	function dummy() {}
 	EOF
+	if test_have_prereq FUNNYNAMES
+	then
+		echo unusual >"\"unusual\" pathname" &&
+		echo unusual >"t/nested \"unusual\" pathname"
+	fi &&
 	git add . &&
 	test_tick &&
 	git commit -m initial
@@ -481,6 +486,48 @@ do
 		git grep --count -h -e b $H -- ab >actual &&
 		test_cmp expected actual
 	'
+
+	test_expect_success FUNNYNAMES "grep $L should quote unusual pathnames" '
+		cat >expected <<-EOF &&
+		${HC}"\"unusual\" pathname":unusual
+		${HC}"t/nested \"unusual\" pathname":unusual
+		EOF
+		git grep unusual $H >actual &&
+		test_cmp expected actual
+	'
+
+	test_expect_success FUNNYNAMES "grep $L in subdir should quote unusual relative pathnames" '
+		cat >expected <<-EOF &&
+		${HC}"nested \"unusual\" pathname":unusual
+		EOF
+		(
+			cd t &&
+			git grep unusual $H
+		) >actual &&
+		test_cmp expected actual
+	'
+
+	test_expect_success FUNNYNAMES "grep -z $L with unusual pathnames" '
+		cat >expected <<-EOF &&
+		${HC}"unusual" pathname:unusual
+		${HC}t/nested "unusual" pathname:unusual
+		EOF
+		git grep -z unusual $H >actual &&
+		tr "\0" ":" <actual >actual-replace-null &&
+		test_cmp expected actual-replace-null
+	'
+
+	test_expect_success FUNNYNAMES "grep -z $L in subdir with unusual relative pathnames" '
+		cat >expected <<-EOF &&
+		${HC}nested "unusual" pathname:unusual
+		EOF
+		(
+			cd t &&
+			git grep -z unusual $H
+		) >actual &&
+		tr "\0" ":" <actual >actual-replace-null &&
+		test_cmp expected actual-replace-null
+	'
 done
 
 cat >expected <<EOF