Replace WebAssembly feature CLI options with --wasm-features.

This commit hides the existing WebAssembly feature CLI options (e.g.
`--enable-simd`) and adds a `--wasm-features` flag that enables multiple
(or all) WebAssembly features.

Features can be disabled by prefixing the value with `-`, e.g.
`--wasm-features=-simd`.

src/commands/compile.rs

@@ -12,6 +12,31 @@ use structopt::{
 use target_lexicon::Triple;
 use wasmtime::{Config, Engine, Module};
 
+lazy_static::lazy_static! {
+    static ref AFTER_HELP: String = {
+        format!(
+            "By default, no CPU features or presets will be enabled for the compilation.\n\
+            \n\
+            {}\
+            \n\
+            Usage examples:\n\
+            \n\
+            Compiling a WebAssembly module for the current platform:\n\
+            \n  \
+            wasmtime compile example.wasm
+            \n\
+            Specifying the output file:\n\
+            \n  \
+            wasmtime compile -o output.cwasm input.wasm\n\
+            \n\
+            Compiling for a specific platform (Linux) and CPU preset (Skylake):\n\
+            \n  \
+            wasmtime compile --target x86_64-unknown-linux --skylake foo.wasm\n",
+            crate::WASM_FEATURES.as_str()
+        )
+    };
+}
+
 /// Compiles a WebAssembly module.
 #[derive(StructOpt)]
 #[structopt(
@@ -22,23 +47,7 @@ use wasmtime::{Config, Engine, Module};
     group = ArgGroup::with_name("preset-x64"),
     group = ArgGroup::with_name("aarch64").multiple(true).conflicts_with_all(&["x64", "preset-x64"]),
     group = ArgGroup::with_name("preset-aarch64").conflicts_with_all(&["x64", "preset-x64"]),
-    after_help = "By default, no CPU flags will be enabled for the compilation.\n\
-                  \n\
-                  Use the various preset and CPU flag options for the environment being targeted.\n\
-                  \n\
-                  Usage examples:\n\
-                  \n\
-                  Compiling a WebAssembly module for the current platform:\n\
-                  \n  \
-                  wasmtime compile example.wasm
-                  \n\
-                  Specifying the output file:\n\
-                  \n  \
-                  wasmtime compile -o output.cwasm input.wasm\n\
-                  \n\
-                  Compiling for a specific platform (Linux) and CPU preset (Skylake):\n\
-                  \n  \
-                  wasmtime compile --target x86_64-unknown-linux --skylake foo.wasm\n"
+    after_help = AFTER_HELP.as_str()
 )]
 pub struct CompileCommand {
     #[structopt(flatten)]

src/commands/run.rs

@@ -68,9 +68,15 @@ fn parse_preloads(s: &str) -> Result<(String, PathBuf)> {
     Ok((parts[0].into(), parts[1].into()))
 }
 
+lazy_static::lazy_static! {
+    static ref AFTER_HELP: String = {
+        crate::WASM_FEATURES.to_string()
+    };
+}
+
 /// Runs a WebAssembly module
 #[derive(StructOpt)]
-#[structopt(name = "run", setting = AppSettings::TrailingVarArg)]
+#[structopt(name = "run", setting = AppSettings::TrailingVarArg, after_help = AFTER_HELP.as_str())]
 pub struct RunCommand {
     #[structopt(flatten)]
     common: CommonOptions,

src/commands/wasm2obj.rs

@@ -11,9 +11,17 @@ use std::{
 use structopt::{clap::AppSettings, StructOpt};
 use target_lexicon::Triple;
 
-/// The after help text for the `wasm2obj` command.
-pub const WASM2OBJ_AFTER_HELP: &str = "The translation is dependent on the environment chosen.\n\
-     The default is a dummy environment that produces placeholder values.";
+lazy_static::lazy_static! {
+    static ref AFTER_HELP: String = {
+        format!(
+            "The translation is dependent on the environment chosen.\n\
+            The default is a dummy environment that produces placeholder values.\n\
+            \n\
+            {}",
+            crate::WASM_FEATURES.as_str()
+        )
+    };
+}
 
 /// Translates a WebAssembly module to native object file
 #[derive(StructOpt)]
@@ -21,7 +29,7 @@ pub const WASM2OBJ_AFTER_HELP: &str = "The translation is dependent on the envir
     name = "wasm2obj",
     version = env!("CARGO_PKG_VERSION"),
     setting = AppSettings::ColoredHelp,
-    after_help = WASM2OBJ_AFTER_HELP,
+    after_help = AFTER_HELP.as_str(),
 )]
 pub struct WasmToObjCommand {
     #[structopt(flatten)]

src/commands/wast.rs

@@ -7,12 +7,19 @@ use structopt::{clap::AppSettings, StructOpt};
 use wasmtime::{Engine, Store};
 use wasmtime_wast::WastContext;
 
+lazy_static::lazy_static! {
+    static ref AFTER_HELP: String = {
+        crate::WASM_FEATURES.to_string()
+    };
+}
+
 /// Runs a WebAssembly test script file
 #[derive(StructOpt)]
 #[structopt(
     name = "wast",
     version = env!("CARGO_PKG_VERSION"),
     setting = AppSettings::ColoredHelp,
+    after_help = AFTER_HELP.as_str(),
 )]
 pub struct WastCommand {
     #[structopt(flatten)]