Group --emit-cfg, --emit-llvm, --emit-bc, --emit-object into single --emit

Signed-off-by: Sean Young <sean@mess.org>

src/main.rs

@@ -59,34 +59,16 @@ fn main() {
                 .multiple(true),
         )
         .arg(
-            Arg::with_name("CFG")
-                .help("emit Control Flow Graph")
-                .long("emit-cfg")
-                .group("EMIT"),
-        )
-        .arg(
-            Arg::with_name("LLVM")
-                .help("emit llvm IR rather than WASM")
-                .long("emit-llvm")
-                .group("EMIT"),
-        )
-        .arg(
-            Arg::with_name("LLVM-BC")
-                .help("emit llvm BC rather than WASM")
-                .long("emit-bc")
-                .group("EMIT"),
-        )
-        .arg(
-            Arg::with_name("OBJECT")
-                .help("emit WASM object file")
-                .long("emit-object")
-                .group("EMIT"),
+            Arg::with_name("EMIT")
+                .help("Emit compiler state at early stage")
+                .long("emit")
+                .takes_value(true)
+                .possible_values(&["cfg", "llvm", "bc", "object"]),
         )
         .arg(
             Arg::with_name("STD-JSON")
                 .help("mimic solidity json output on stdout")
                 .long("standard-json")
-                .group("EMIT"),
         )
         .arg(
             Arg::with_name("VERBOSE")
@@ -158,7 +140,7 @@ fn main() {
 
         // emit phase
         for contract in &contracts {
-            if matches.is_present("CFG") {
+            if let Some("cfg") = matches.value_of("EMIT") {
                 println!("{}", contract.to_string());
                 continue;
             }
@@ -167,12 +149,12 @@ fn main() {
 
             let contract = emit::Contract::new(contract, &filename);
 
-            if matches.is_present("LLVM") {
+            if let Some("llvm") = matches.value_of("EMIT") {
                 contract.dump_llvm();
                 continue;
             }
 
-            if matches.is_present("LLVM-BC") {
+            if let Some("bc") = matches.value_of("EMIT") {
                 let bc = contract.bitcode();
                 let bc_filename = output_file(&contract.name, "bc");
 
@@ -189,7 +171,7 @@ fn main() {
                 }
             };
 
-            if matches.is_present("OBJECT") {
+            if let Some("object") = matches.value_of("EMIT") {
                 let obj_filename = output_file(&contract.name, "o");
 
                 let mut file = File::create(obj_filename).unwrap();