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

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

third_party/git/t/chainlint/subshell-here-doc.test

@@ -0,0 +1,39 @@
+(
+# LINT: stitch together incomplete \-ending lines
+# LINT: swallow here-doc to avoid false positives in content
+	echo wobba \
+	       gorgo snoot \
+	       wafta snurb <<-EOF &&
+	quoth the raven,
+	nevermore...
+	EOF
+
+# LINT: missing "&&" on 'cat'
+	cat <<EOF >bip
+	fish fly high
+	EOF
+
+# LINT: swallow here-doc (EOF is last line of subshell)
+	echo <<-\EOF >bop
+	gomez
+	morticia
+	wednesday
+	pugsly
+	EOF
+) &&
+(
+# LINT: swallow here-doc with arbitrary tag
+	cat <<-\ARBITRARY >bup &&
+	glink
+	FIZZ
+	ARBITRARY
+	cat <<-'ARBITRARY2' >bup2 &&
+	glink
+	FIZZ
+	ARBITRARY2
+	cat <<-"ARBITRARY3" >bup3 &&
+	glink
+	FIZZ
+	ARBITRARY3
+	meep
+)