Revert "Generate Rust files from protobuf files on each build"

This reverts commit f64a16a.

.gitignore

@@ -3,7 +3,6 @@
 *~
 
 target/
-sticker-tf-proto/src/*.rs
 
 .eggs
 __pycache__

.travis.yml

@@ -1,15 +1,11 @@
-dist: bionic
+dist: xenial
 env:
   global:
   - PROJECT_NAME: sticker
 addons:
   apt:
     packages:
     - patchelf
-    - protobuf-compiler
-  homebrew:
-    packages:
-    - protobuf
 matrix:
   fast_finish: true
   include:

sticker-tf-proto/Cargo.toml

@@ -10,7 +10,13 @@ repository = "https://github.com/danieldk/sticker.git"
 license = "Apache-2.0"
 
 [dependencies]
-protobuf = "2"
+# This is annoying, but the generated protobuf contains
+# the version number in symbols and compilation fails when
+# this dependency is updated
+protobuf = "= 2.8.0"
 
 [build-dependencies]
-protoc-rust = "2"
+protoc-rust = { version = "2", optional = true }
+
+[features]
+proto-compile = [ "protoc-rust" ]

sticker-tf-proto/build.rs

@@ -1,4 +1,5 @@
 fn main() {
+    #[cfg(feature = "proto-compile")]
     protoc_rust::run(protoc_rust::Args {
         out_dir: "src",
         input: &[