design: stub out basic subcommands using clap

The details aren't fleshed out yet but this should put a little
more meat on the bones for review.

Signed-off-by: Paul Osborne <[email protected]>

Author: posborne

.travis.yml

@@ -0,0 +1,16 @@
+language: rust
+sudo: false
+
+rust:
+  - 1.2.0
+  - 1.3.0
+  - 1.4.0
+  - 1.5.0
+  - 1.6.0
+  - stable
+  - beta
+  - nightly
+
+script:
+  - cargo test
+  - cargo doc

Cargo.lock

@@ -4,3 +4,5 @@ version = "0.1.0"
 authors = ["Paul Osborne <[email protected]>"]
 
 [dependencies]
+sysfs_gpio = "0.4.0"
+clap = "2.2"

Cargo.toml

@@ -1,3 +1,38 @@
+extern crate clap;
+
+use clap::{Arg, App, SubCommand};
+
 fn main() {
-    println!("Hello, world!");
+    let gpio_cmd_matches = App::new("GPIO Utils")
+        .version(env!("CARGO_PKG_VERSION"))
+        .about("Read, Write, and Configure GPIOs")
+        .subcommand(SubCommand::with_name("read")
+                    .about("Read the value of a GPIO Input"))
+        .subcommand(SubCommand::with_name("poll")
+                    .about("Wait for an event to happen on an GPIO Input"))
+        .subcommand(SubCommand::with_name("write")
+                    .about("Write the value of a GPIO Output"))
+        .subcommand(SubCommand::with_name("export")
+                    .about("Export a given GPIO"))
+        .subcommand(SubCommand::with_name("export-all")
+                    .about("Export all configured GPIOs"))
+        .subcommand(SubCommand::with_name("unexport")
+                    .about("Unexport a given GPIO"))
+        .subcommand(SubCommand::with_name("unexport-all")
+                    .about("Unexport all configured, exported GPIOs"))
+        .subcommand(SubCommand::with_name("status")
+                    .about("Output status of all configured GPIOs"))
+        .get_matches();
+
+    match gpio_cmd_matches.subcommand() {
+        ("read", Some(m)) => {},
+        ("poll", Some(m)) => {},
+        ("write", Some(m)) => {},
+        ("export", Some(m)) => {},
+        ("export-all", Some(m)) => {},
+        ("unexport", Some(m)) => {},
+        ("unexport-all", Some(m)) => {},
+        ("status", Some(m)) => {},
+        _ => {}
+    }
 }