Add more explicit help and readme

README.md

@@ -0,0 +1,20 @@
+# Advent of Code 2019
+
+> More info : https://adventofcode.com/2019
+
+## Usage
+
+```
+Advent of Code 2019 0.1
+
+USAGE:
+    advent_of_code_2019 --challenge <CHALLENGE> --input <INPUT>
+
+FLAGS:
+    -h, --help       Prints help information
+    -V, --version    Prints version information
+
+OPTIONS:
+    -c, --challenge <CHALLENGE>    Challenge id from 1 (1st day, 1st part) to 50 (25th day, 2nd part).
+    -i, --input <INPUT>            Input file, ex `input/day1`.
+```

src/main.rs

@@ -13,6 +13,7 @@ fn main() {
             .short("c")
             .long("challenge")
             .value_name("CHALLENGE")
+            .help("Challenge id from 1 (1st day, 1st part) to 50 (25th day, 2nd part).")
             .required(true)
             .takes_value(true)
             .min_values(1)
@@ -21,6 +22,7 @@ fn main() {
             .short("i")
             .long("input")
             .value_name("INPUT")
+            .help("Input file, ex `input/day1`.")
             .required(true)
             .takes_value(true))
         .get_matches();