Define theme by presence of "dark" or "light" entries in git config,

and give the ability to filter themes shown with --show-themes by
dark or light, using the --dark and --light flags

4 files changed, 39 insertions, 21 deletions

diff --git a/src/cli.rs b/src/cli.rs
index 781fd644..60a4d5a7 100644
--- a/src/cli.rs
+++ b/src/cli.rs
@@ -201,11 +201,13 @@ https://github.com/dandavison/delta/issues.
 pub struct Opt {
     /// Use default colors appropriate for a light terminal background. For more control, see the
     /// style options and --syntax-theme.
+    /// When passed in with --show-themes, only light themes will be displayed.
     #[structopt(long = "light")]
     pub light: bool,
 
     /// Use default colors appropriate for a dark terminal background. For more control, see the
     /// style options and --syntax-theme.
+    /// When passed in with --show-themes, only dark themes will be displayed.
     #[structopt(long = "dark")]
     pub dark: bool,
 
@@ -272,6 +274,8 @@ pub struct Opt {
     /// Show all available delta themes, each with an example of highlighted diff output.
     /// If diff output is supplied on standard input then this will be used for the demo. For
     /// example: `git show --color=always | delta --show-themes`.
+    /// When used with the --dark or --light command line arguments, will only show dark or
+    /// light themes, respectively.
     #[structopt(long = "show-themes")]
     pub show_themes: bool,
 
diff --git a/src/main.rs b/src/main.rs
index fb4628ed..dcc6ed48 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -68,7 +68,7 @@ fn run_app() -> std::io::Result<i32> {
         show_syntax_themes()?;
         return Ok(0);
     } else if opt.show_themes {
-        show_themes()?;
+        show_themes(opt.dark, opt.light)?;
         return Ok(0);
     }
 
@@ -312,7 +312,7 @@ where
     }
 }
 
-fn show_themes() -> std::io::Result<()> {
+fn show_themes(dark: bool, light: bool) -> std::io::Result<()> {
     use bytelines::ByteLines;
     use sample_diff::DIFF;
     use std::io::BufReader;
@@ -337,17 +337,23 @@ fn show_themes() -> std::io::Result<()> {
     let writer = output_type.handle().unwrap();
 
     for theme in &get_themes(git_config::GitConfig::try_create()) {
-        writeln!(writer, "\n\nTheme: {}\n", title_style.paint(theme))?;
         let opt =
             cli::Opt::from_iter_and_git_config(&["", "", "--features", &theme], &mut git_config);
+        let is_dark_theme = opt.dark;
+        let is_light_theme = opt.light;
         let config = config::Config::from(opt);
 
-        if let Err(error) = delta(ByteLines::new(BufReader::new(&input[0..])), writer, &config) {
-            match error.kind() {
-                ErrorKind::BrokenPipe => process::exit(0),
-                _ => eprintln!("{}", error),
+        if (dark && is_dark_theme) || (light && is_light_theme) || (!dark && !light) {
+            writeln!(writer, "\n\nTheme: {}\n", title_style.paint(theme))?;
+
+            if let Err(error) = delta(ByteLines::new(BufReader::new(&input[0..])), writer, &config)
+            {
+                match error.kind() {
+                    ErrorKind::BrokenPipe => process::exit(0),
+                    _ => eprintln!("{}", error),
+                }
             }
-        };
+        }
     }
 
     Ok(())
diff --git a/src/options/get.rs b/src/options/get.rs
index 58209f5d..a1bbecae 100644
--- a/src/options/get.rs
+++ b/src/options/get.rs
@@ -41,7 +41,7 @@ where
 }
 
 lazy_static! {
-    static ref GIT_CONFIG_THEME_REGEX: Regex = Regex::new(r"^delta\.(.+)\.is-theme$").unwrap();
+    static ref GIT_CONFIG_THEME_REGEX: Regex = Regex::new(r"^delta\.(.+)\.(light|dark)$").unwrap();
 }
 
 pub fn get_themes(git_config: Option<git_config::GitConfig>) -> Vec<String> {
@@ -53,9 +53,10 @@ pub fn get_themes(git_config: Option<git_config::GitConfig>) -> Vec<String> {
         if entry_value == "true" {
             let caps = GIT_CONFIG_THEME_REGEX.captures(entry_name);
             if let Some(caps) = caps {
-                // need to check value i.e. whether is_theme = false
                 let name = caps.get(1).map_or("", |m| m.as_str()).to_string();
-                themes.push(name)
+                if !themes.contains(&name) {
+                    themes.push(name)
+                }
             }
         }
     }
@@ -304,15 +305,20 @@ pub mod tests {
     #[test]
     fn test_get_themes_from_config() {
         let git_config_contents = b"
-[delta \"yes\"]
+[delta \"dark-theme\"]
     max-line-distance = 0.6
-    is-theme = true
+    dark = true
 
-[delta \"not-a-theme\"]
+[delta \"light-theme\"]
+    max-line-distance = 0.6
+    light = true
+
+[delta \"light-and-dark-theme\"]
     max-line-distance = 0.6
-    is-theme = false
+    light = true
+    dark = true
 
-[delta \"has-no-theme-entry\"]
+[delta \"not-a-theme\"]
     max-line-distance = 0.6
 ";
         let git_config_path = "delta__test_get_themes_git_config.gitconfig";
@@ -325,7 +331,10 @@ pub mod tests {
 
         let themes = get_themes(git_config);
 
-        assert_eq!(themes, ["yes"]);
+        assert_eq!(
+            themes,
+            ["dark-theme", "light-theme", "light-and-dark-theme"]
+        );
 
         remove_file(git_config_path).unwrap();
     }
diff --git a/themes.gitconfig b/themes.gitconfig
index 3dd4ba1a..68783e9c 100644
--- a/themes.gitconfig
+++ b/themes.gitconfig
@@ -49,10 +49,10 @@
     file-modified-label = [M]
     file-removed-label = [-]
     file-renamed-label = [R]
-    is-theme = true
 
 [delta "villsau"]
     # author: https://github.com/torarnv
+    dark = true
     syntax-theme = OneHalfDark
     line-numbers = false
     hunk-header-style = file line-number syntax
@@ -70,11 +70,11 @@
     plus-emph-style = bold green 22
     plus-empty-line-marker-style = normal "#002800"
     whitespace-error-style = reverse red
-    is-theme = true
 
 [delta "collared-trogon"]
     # author: https://github.com/clnoll
     commit-decoration-style = bold box ul
+    dark = true
     file-style = omit
     file-decoration-style = none
     hunk-header-style = file line-number syntax
@@ -92,11 +92,11 @@
     plus-style = syntax "#001a00"
     plus-emph-style = syntax "#003300"
     syntax-theme = Nord
-    is-theme = true
 
 [delta "tangara-chilensis"]
     # author: https://github.com/clnoll
     commit-decoration-style = bold box ul "#34fd50"
+    dark = true
     file-style = omit
     file-decoration-style = none
     hunk-header-style = file line-number syntax
@@ -115,4 +115,3 @@
     plus-emph-style = syntax "#03a4ff"
     side-by-side = true
     syntax-theme = Vibrant Sunburst
-    is-theme = true