Add msysGit's helper to upload to GitHub

This was taken from msysgit/msysgit@00039af4
(Rewrite upload-to-github.sh for current GitHub API).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

upload-to-github.sh

@@ -0,0 +1,45 @@
+#!/bin/sh
+
+die () {
+	echo "$*" >&2
+	exit 1
+}
+
+test $# -ge 2 ||
+die "Usage: $0 <tag-name> <path>..."
+
+tagname="$1"
+shift
+
+url=https://api.github.com/repos/msysgit/msysgit/releases
+id="$(curl --netrc -s $url |
+	grep -B1 "\"tag_name\": \"$tagname\"" |
+	sed -n 's/.*"id": *\([0-9]*\).*/\1/p')"
+test -n "$id" || {
+	out="$(curl --netrc -s -XPOST -d '{"tag_name":"'"$tagname"'"}' $url)" ||
+	die "Error creating release: $out"
+	id="$(echo "$out" |
+		sed -n 's/.*"id": *\([0-9]*\).*/\1/p')"
+	test -n "$id" ||
+	die "Could not create release for tag $tagname"
+}
+
+url=https://uploads.${url#https://api.}
+
+for path
+do
+	case "$path" in
+	*.exe)
+		contenttype=application/executable
+		;;
+	*.7z)
+		contenttype=application/zip
+		;;
+	*)
+		die "Unknown file type: $path"
+		;;
+	esac
+	basename="$(basename "$path")"
+	curl -i --netrc -XPOST -H "Content-Type: $contenttype" \
+		--data-binary @"$path" "$url/$id/assets?name=$basename"
+done