Capture env var configurations using clap

Parses env configurations into matches (for those that can be configured
via matches) instead of relying on dedicated env checks everywhere.

Fixes sharkdp#1152

src/bin/bat/app.rs

@@ -1,7 +1,6 @@
 use std::collections::HashSet;
 use std::env;
 use std::ffi::OsStr;
-use std::str::FromStr;
 
 use atty::{self, Stream};
 
@@ -183,7 +182,6 @@ impl App {
                 .matches
                 .value_of("tabs")
                 .map(String::from)
-                .or_else(|| env::var("BAT_TABS").ok())
                 .and_then(|t| t.parse().ok())
                 .unwrap_or(
                     if style_components.plain() && paging_mode == PagingMode::Never {
@@ -196,7 +194,6 @@ impl App {
                 .matches
                 .value_of("theme")
                 .map(String::from)
-                .or_else(|| env::var("BAT_THEME").ok())
                 .map(|s| {
                     if s == "default" {
                         String::from(HighlightingAssets::default_theme())
@@ -296,16 +293,6 @@ impl App {
             } else if matches.is_present("plain") {
                 [StyleComponent::Plain].iter().cloned().collect()
             } else {
-                let env_style_components: Option<Vec<StyleComponent>> = env::var("BAT_STYLE")
-                    .ok()
-                    .map(|style_str| {
-                        style_str
-                            .split(',')
-                            .map(|x| StyleComponent::from_str(&x))
-                            .collect::<Result<Vec<StyleComponent>>>()
-                    })
-                    .transpose()?;
-
                 matches
                     .value_of("style")
                     .map(|styles| {
@@ -315,7 +302,6 @@ impl App {
                             .filter_map(|style| style.ok())
                             .collect::<Vec<_>>()
                     })
-                    .or(env_style_components)
                     .unwrap_or_else(|| vec![StyleComponent::Full])
                     .into_iter()
                     .map(|style| style.components(self.interactive_output))

src/bin/bat/clap_app.rs

@@ -151,6 +151,7 @@ pub fn build_app(interactive_output: bool) -> ClapApp<'static, 'static> {
     app = app.arg(
         Arg::with_name("tabs")
             .long("tabs")
+			.env("BAT_TABS")
             .overrides_with("tabs")
             .takes_value(true)
             .value_name("T")
@@ -303,6 +304,7 @@ pub fn build_app(interactive_output: bool) -> ClapApp<'static, 'static> {
         .arg(
             Arg::with_name("pager")
                 .long("pager")
+				.env("BAT_PAGER")
                 .overrides_with("pager")
                 .takes_value(true)
                 .value_name("command")
@@ -335,6 +337,7 @@ pub fn build_app(interactive_output: bool) -> ClapApp<'static, 'static> {
         .arg(
             Arg::with_name("theme")
                 .long("theme")
+				.env("BAT_THEME")
                 .overrides_with("theme")
                 .takes_value(true)
                 .help("Set the color theme for syntax highlighting.")
@@ -356,6 +359,7 @@ pub fn build_app(interactive_output: bool) -> ClapApp<'static, 'static> {
             Arg::with_name("style")
                 .long("style")
                 .value_name("components")
+				.env("BAT_STYLE")
                 // Need to turn this off for overrides_with to work as we want. See the bottom most
                 // example at https://docs.rs/clap/2.32.0/clap/struct.Arg.html#method.overrides_with
                 .use_delimiter(false)

src/output.rs

@@ -36,20 +36,16 @@ impl OutputType {
 
         let mut replace_arguments_to_less = false;
 
-        let pager_from_env = match (env::var("BAT_PAGER"), env::var("PAGER")) {
-            (Ok(bat_pager), _) => Some(bat_pager),
-            (_, Ok(pager)) => {
-                // less needs to be called with the '-R' option in order to properly interpret the
-                // ANSI color sequences printed by bat. If someone has set PAGER="less -F", we
-                // therefore need to overwrite the arguments and add '-R'.
-                //
-                // We only do this for PAGER (as it is not specific to 'bat'), not for BAT_PAGER
-                // or bats '--pager' command line option.
-                replace_arguments_to_less = true;
-                Some(pager)
-            }
-            _ => None,
-        };
+        let pager_from_env = env::var("PAGER").ok().map(|pager| {
+            // less needs to be called with the '-R' option in order to properly interpret the
+            // ANSI color sequences printed by bat. If someone has set PAGER="less -F", we
+            // therefore need to overwrite the arguments and add '-R'.
+            //
+            // We only do this for PAGER (as it is not specific to 'bat'), not for BAT_PAGER
+            // or bats '--pager' command line option.
+            replace_arguments_to_less = true;
+            pager
+        });
 
         let pager_from_config = pager_from_config.map(|p| p.to_string());
 

tests/integration_tests.rs

@@ -381,6 +381,17 @@ fn pager_basic() {
         .stdout(predicate::eq("pager-output\n").normalize());
 }
 
+#[test]
+fn pager_config() {
+    bat()
+        .arg("--pager=echo pager-output")
+        .arg("--paging=always")
+        .arg("test.txt")
+        .assert()
+        .success()
+        .stdout(predicate::eq("pager-output\n").normalize());
+}
+
 #[test]
 fn pager_overwrite() {
     bat()
@@ -393,6 +404,19 @@ fn pager_overwrite() {
         .stdout(predicate::eq("pager-output\n").normalize());
 }
 
+#[test]
+fn pager_overwrite_overwrite() {
+    bat()
+        .env("PAGER", "echo other-pager")
+        .env("BAT_PAGER", "echo another-pager")
+        .arg("--pager=echo pager-output")
+        .arg("--paging=always")
+        .arg("test.txt")
+        .assert()
+        .success()
+        .stdout(predicate::eq("pager-output\n").normalize());
+}
+
 #[test]
 fn pager_disable() {
     bat()