Add optional build script for `protoc-rust`

build_proto.rs

@@ -0,0 +1,25 @@
+//! To regenerate *.rs files in `src/proto/` rename this file to `build.rs`
+//! and add this to `Cargo.toml`:
+//! ```
+//! [build-dependencies]
+//! protoc-rust = "2.0"
+//! ```
+
+extern crate protoc_rust;
+
+fn main() {
+    let proto_files = ["src/proto/fileformat.proto", "src/proto/osmformat.proto"];
+
+    for path in &proto_files {
+        println!("cargo:rerun-if-changed={}", path);
+    }
+
+    protoc_rust::run(protoc_rust::Args {
+        out_dir: "src/proto",
+        input: &proto_files,
+        customize: protoc_rust::Customize {
+            ..Default::default()
+        },
+        includes: &[],
+    }).expect("protoc");
+}