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

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

third_party/git/Documentation/technical/api-index.sh

@@ -0,0 +1,28 @@
+#!/bin/sh
+
+(
+	c=////////////////////////////////////////////////////////////////
+	skel=api-index-skel.txt
+	sed -e '/^\/\/ table of contents begin/q' "$skel"
+	echo "$c"
+
+	ls api-*.txt |
+	while read filename
+	do
+		case "$filename" in
+		api-index-skel.txt | api-index.txt) continue ;;
+		esac
+		title=$(sed -e 1q "$filename")
+		html=${filename%.txt}.html
+		echo "* link:$html[$title]"
+	done
+	echo "$c"
+	sed -n -e '/^\/\/ table of contents end/,$p' "$skel"
+) >api-index.txt+
+
+if test -f api-index.txt && cmp api-index.txt api-index.txt+ >/dev/null
+then
+	rm -f api-index.txt+
+else
+	mv api-index.txt+ api-index.txt
+fi