Implement version number

Cargo.lock

@@ -47,6 +47,28 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "git-version"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "94918e83f1e01dedc2e361d00ce9487b14c58c7f40bab148026fa39d42cb41e2"
+dependencies = [
+ "git-version-macro",
+ "proc-macro-hack",
+]
+
+[[package]]
+name = "git-version-macro"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "34a97a52fdee1870a34fa6e4b77570cba531b27d1838874fef4429a791a3d657"
+dependencies = [
+ "proc-macro-hack",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "gmp-mpfr-sys"
 version = "1.4.5"
@@ -108,6 +130,7 @@ name = "opentally"
 version = "0.1.0"
 dependencies = [
  "clap",
+ "git-version",
  "num-traits",
  "rug",
 ]
@@ -142,6 +165,12 @@ dependencies = [
  "version_check",
 ]
 
+[[package]]
+name = "proc-macro-hack"
+version = "0.5.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dbf0c48bc1d91375ae5c3cd81e3722dff1abcf81a30960240640d223f59fe0e5"
+
 [[package]]
 name = "proc-macro2"
 version = "1.0.27"

Cargo.toml

@@ -5,6 +5,7 @@ authors = ["Lee Yingtong Li <runassudo@yingtongli.me>"]
 edition = "2018"
 
 [dependencies]
+git-version = "0.3.4"
 num-traits = "0.2"
 
 [dependencies.rug]

src/main.rs

@@ -23,11 +23,16 @@ use crate::election::{CandidateState, CountState, CountStateOrRef, Election, Sta
 use crate::numbers::{Number, NumType};
 
 use clap::Clap;
+use git_version::git_version;
 
 use std::fs::File;
 use std::io::{self, BufRead};
 
+const VERSION: &str = git_version!(args=["--always", "--dirty=-dev"], fallback="unknown");
+
+/// Open-source election vote counting
 #[derive(Clap)]
+#[clap(name="OpenTally", version=VERSION)]
 struct Opts {
 	#[clap(subcommand)]
 	command: Command,