merge(third_party/git): Merge squashed git subtree at v2.23.0

Merge commit '1b593e1ea4' as 'third_party/git'

third_party/git/t/chainlint/multi-line-string.test

@@ -0,0 +1,27 @@
+(
+	x="line 1
+		line 2
+		line 3" &&
+# LINT: missing "&&" on assignment
+	y='line 1
+		line2'
+	foobar
+) &&
+(
+# LINT: apostrophe (in a contraction) within string not misinterpreted as
+# LINT: starting multi-line single-quoted string
+	echo "there's nothing to see here" &&
+	exit
+) &&
+(
+	echo "xyz" "abc
+		def
+		ghi" &&
+	echo 'xyz' 'abc
+		def
+		ghi' &&
+	echo 'xyz' "abc
+		def
+		ghi" &&
+	barfoo
+)