Use a custom env var for log settings intead of default RUST_LOG

Author: peterjoel

src/format-diff/main.rs

@@ -61,7 +61,7 @@ pub struct Opts {
 }
 
 fn main() {
-    env_logger::init();
+    env_logger::Builder::from_env("RUSTFMT_LOG").init();
     let opts = Opts::from_args();
     if let Err(e) = run(opts) {
         println!("{}", e);

src/git-rustfmt/main.rs

@@ -133,7 +133,7 @@ struct Opt {
 }
 
 fn main() {
-    env_logger::init();
+    env_logger::Builder::from_env("RUSTFMT_LOG").init();
 
     let opt: Opt = Opt::from_args();
 

src/rustfmt/main.rs

@@ -20,7 +20,7 @@ use rustfmt_nightly::{
 };
 
 fn main() {
-    env_logger::init();
+    env_logger::Builder::from_env("RUSTFMT_LOG").init();
 
     let opt: Opt = Opt::from_args();