Add dummy package for C sources directories to allow vendoring

To allow 'go mod -vendor' to take directories, we create dummy packages
in each directory.

Basically it does:
for d in $(find internal -type d); do echo "package $(basename $d)" >"$d/pkg.go"; done

A script is used to maintained those dummy package besides hidapi/libusb
upgrades: internal/dummy-packages.sh

See:
- karalabe#31
- golang/go#26366

internal.go

@@ -0,0 +1,5 @@
+package hid
+
+// Just for Go vendoring
+// See https://github.com/golang/go/issues/26366
+import _ "github.com/dolmen-go/hid/internal"

internal/dummy-packages.sh

@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+cd "$(dirname "$0")"
+
+for d in $(find libusb hidapi -type d)
+do
+	echo "package $(basename $d)" >"$d/pkg.go"
+done
+
+pkg=$(cd ..; go list)/internal
+
+{
+	echo 'package internal'
+	echo
+	echo 'import ('
+	for d in $(find hidapi libusb -type d);
+	do
+		printf '\t_ "%s/%s"\n' "$pkg" "$d"
+	done
+	echo ')'
+} >pkg.go

internal/hidapi/hidapi/pkg.go

@@ -0,0 +1 @@
+package hidapi

internal/hidapi/libusb/pkg.go

@@ -0,0 +1 @@
+package libusb

internal/hidapi/mac/pkg.go

@@ -0,0 +1 @@
+package mac

internal/hidapi/pkg.go

@@ -0,0 +1 @@
+package hidapi

internal/hidapi/windows/pkg.go

@@ -0,0 +1 @@
+package windows

internal/libusb/libusb/os/pkg.go

@@ -0,0 +1 @@
+package os

internal/libusb/libusb/pkg.go

@@ -0,0 +1 @@
+package libusb

internal/libusb/pkg.go

@@ -0,0 +1 @@
+package libusb

internal/pkg.go

@@ -0,0 +1,12 @@
+package internal
+
+import (
+	_ "github.com/dolmen-go/hid/internal/hidapi"
+	_ "github.com/dolmen-go/hid/internal/hidapi/mac"
+	_ "github.com/dolmen-go/hid/internal/hidapi/hidapi"
+	_ "github.com/dolmen-go/hid/internal/hidapi/windows"
+	_ "github.com/dolmen-go/hid/internal/hidapi/libusb"
+	_ "github.com/dolmen-go/hid/internal/libusb"
+	_ "github.com/dolmen-go/hid/internal/libusb/libusb"
+	_ "github.com/dolmen-go/hid/internal/libusb/libusb/os"
+)

internal/upgrade-hidapi.sh

@@ -32,3 +32,5 @@ if [[ -d hidapi ]]; then
 fi
 mv $dir hidapi
 rm -Rf hidapi.orig "$archive"
+
+./dummy-packages.sh

internal/upgrade-libusb.sh

@@ -30,3 +30,5 @@ if [[ -d libusb ]]; then
 fi
 mv libusb-${version} libusb
 rm -Rf libusb.orig "$archive"
+
+./dummy-packages.sh