Add simple configuration file

This allows users to create simple configuration file
(`~/.config/bat/config` on Linux) that has the following format:

    ```bash
    --flag1
    --flag2
    --option1=value1
    # lines beginning with '#' are ignored
    --option2=value2
    # empty lines and trailing whitespace are also ignored

    --option3=value3
    ```

src/app.rs

@@ -14,6 +14,7 @@ use console::Term;
 use ansi_term;
 
 use assets::BAT_THEME_DEFAULT;
+use config::get_args_from_config_file;
 use errors::*;
 use inputfile::InputFile;
 use line_range::LineRange;
@@ -97,7 +98,26 @@ impl App {
     }
 
     fn matches(interactive_output: bool) -> ArgMatches<'static> {
-        clap_app::build_app(interactive_output).get_matches_from(wild::args())
+        let args = if wild::args_os().nth(1) == Some("cache".into()) {
+            // Skip the arguments in bats config file
+
+            wild::args_os().collect::<Vec<_>>()
+        } else {
+            let mut cli_args = wild::args_os();
+
+            // Read arguments from bats config file
+            let mut args = get_args_from_config_file();
+
+            // Put the zero-th CLI argument (program name) first
+            args.insert(0, cli_args.next().unwrap());
+
+            // .. and the rest at the end
+            cli_args.for_each(|a| args.push(a));
+
+            args
+        };
+
+        clap_app::build_app(interactive_output).get_matches_from(args)
     }
 
     pub fn config(&self) -> Result<Config> {

src/assets.rs

@@ -13,11 +13,6 @@ use directories::ProjectDirs;
 use errors::*;
 use inputfile::{InputFile, InputFileReader};
 
-lazy_static! {
-    static ref PROJECT_DIRS: ProjectDirs =
-        ProjectDirs::from("", "", crate_name!()).expect("Could not get home directory");
-}
-
 pub const BAT_THEME_DEFAULT: &str = "Monokai Extended";
 
 pub struct HighlightingAssets {

src/clap_app.rs

@@ -84,6 +84,7 @@ pub fn build_app(interactive_output: bool) -> ClapApp<'static, 'static> {
                 .value_name("style-components")
                 .use_delimiter(true)
                 .takes_value(true)
+                .overrides_with("style")
                 .possible_values(&[
                     "auto", "full", "plain", "changes", "header", "grid", "numbers",
                 ])
@@ -207,6 +208,7 @@ pub fn build_app(interactive_output: bool) -> ClapApp<'static, 'static> {
         .arg(
             Arg::with_name("tabs")
                 .long("tabs")
+                .overrides_with("tabs")
                 .takes_value(true)
                 .value_name("T")
                 .validator(

src/config.rs

@@ -0,0 +1,65 @@
+use std::ffi::OsString;
+use std::fs;
+
+use dirs::PROJECT_DIRS;
+
+pub fn get_args_from_config_file() -> Vec<OsString> {
+    let config_file = PROJECT_DIRS.config_dir().join("config");
+    fs::read_to_string(config_file)
+        .map(|content| get_args_from_str(&content))
+        .unwrap_or(vec![])
+}
+
+fn get_args_from_str<'a>(content: &'a str) -> Vec<OsString> {
+    content
+        .split('\n')
+        .map(|line| line.trim())
+        .filter(|line| !line.is_empty())
+        .filter(|line| !line.starts_with("#"))
+        .map(|line| line.into())
+        .collect()
+}
+
+#[test]
+fn empty() {
+    let args = get_args_from_str("");
+    println!("{:?}", args);
+    assert!(args.is_empty());
+}
+
+#[test]
+fn single() {
+    assert_eq!(vec!["--plain"], get_args_from_str("--plain"));
+}
+
+#[test]
+fn multiple() {
+    let config = "
+    -p
+    --style numbers,changes
+
+    --color=always
+    ";
+    assert_eq!(
+        vec!["-p", "--style numbers,changes", "--color=always"],
+        get_args_from_str(config)
+    );
+}
+
+#[test]
+fn comments() {
+    let config = "
+    # plain style
+    -p
+
+    # show line numbers and Git modifications
+    --style numbers,changes
+
+    # Always show ANSI colors
+    --color=always
+    ";
+    assert_eq!(
+        vec!["-p", "--style numbers,changes", "--color=always"],
+        get_args_from_str(config)
+    );
+}

src/dirs.rs

@@ -0,0 +1,6 @@
+use directories::ProjectDirs;
+
+lazy_static! {
+    pub static ref PROJECT_DIRS: ProjectDirs =
+        ProjectDirs::from("", "", crate_name!()).expect("Could not get home directory");
+}

src/main.rs

@@ -23,9 +23,11 @@ extern crate wild;
 mod app;
 mod assets;
 mod clap_app;
+mod config;
 mod controller;
 mod decorations;
 mod diff;
+mod dirs;
 mod inputfile;
 mod line_range;
 mod output;