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

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

third_party/git/contrib/fast-import/git-import.sh

@@ -0,0 +1,38 @@
+#!/bin/sh
+#
+# Performs an initial import of a directory. This is the equivalent
+# of doing 'git init; git add .; git commit'. It's a lot slower,
+# but is meant to be a simple fast-import example.
+
+if [ -z "$1" -o -z "$2" ]; then
+	echo "usage: git-import branch import-message"
+	exit 1
+fi
+
+USERNAME="$(git config user.name)"
+EMAIL="$(git config user.email)"
+
+if [ -z "$USERNAME" -o -z "$EMAIL" ]; then
+	echo "You need to set user name and email"
+	exit 1
+fi
+
+git init
+
+(
+	cat <<EOF
+commit refs/heads/$1
+committer $USERNAME <$EMAIL> now
+data <<MSGEOF
+$2
+MSGEOF
+
+EOF
+	find * -type f|while read i;do
+		echo "M 100644 inline $i"
+		echo data $(stat -c '%s' "$i")
+		cat "$i"
+		echo
+	done
+	echo
+) | git fast-import --date-format=now