build: include version number in final binary

Use git to parse the tag information, and include it in the output of
`exclave --help`.

Signed-off-by: Sean Cross <sean@xobs.io>

build.rs

@@ -0,0 +1,28 @@
+use std::process::Command;
+
+/// Same as `set_env`, but using `name` as environment variable.
+///
+/// You can, for example, override the `CARGO_PKG_VERSION` using in
+/// your `build.rs` script:
+///
+/// ```
+/// extern crate git_version;
+/// fn main() { git_version::set_env_with_name("CARGO_PKG_VERSION"); }
+/// ```
+fn set_env_with_name(name: &str) {
+    let cmd = Command::new("git")
+        .args(&["describe", "--tags", "--dirty=-modified"])
+        .output()
+        .unwrap();
+    assert!(cmd.status.success());
+    let ver = std::str::from_utf8(&cmd.stdout[..]).unwrap().trim();
+    println!("cargo:rustc-env={}={}", name, ver);
+    println!("cargo:rerun-if-changed=.git/HEAD"); 
+    println!("cargo:rerun-if-changed=.git/index"); 
+    println!("cargo:rerun-if-changed=.git"); 
+    println!("cargo:rerun-if-env-changed={}", name);
+}
+
+fn main() {
+    set_env_with_name("GIT_VERSION");
+}

src/main.rs

@@ -44,7 +44,8 @@ fn main() {
     }).expect("Error setting Ctrl-C handler");
 
     let matches = App::new("Exclave Testing System")
-        .version("1.0")
+        .version(env!("CARGO_PKG_VERSION"))
+        .long_version(env!("GIT_VERSION"))
         .author("Sean Cross <sean@xobs.io>")
         .about("Orchestrates the Common Factory Test Interface server")
         .arg(