3 files changed, 63 insertions, 1 deletions

diff --git a/src/options/get.rs b/src/options/get.rs
index a36987ca..b907ee88 100644
--- a/src/options/get.rs
+++ b/src/options/get.rs
@@ -1,3 +1,5 @@
+use lazy_static::lazy_static;
+use regex::Regex;
 use std::collections::HashMap;
 
 use crate::cli;
@@ -38,6 +40,27 @@ where
     T::get_option_value(option_name, builtin_features, opt, git_config)
 }
 
+lazy_static! {
+    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> {
+    let mut themes: Vec<String> = Vec::new();
+    for e in &git_config.unwrap().config.entries(None).unwrap() {
+        let entry = e.unwrap();
+        let entry_name = entry.name().unwrap();
+        let caps = GIT_CONFIG_THEME_REGEX.captures(entry_name);
+        if let Some(caps) = caps {
+            let name = caps.get(1).map_or("", |m| m.as_str()).to_string();
+            if !themes.contains(&name) {
+                themes.push(name)
+            }
+        }
+    }
+    themes.sort_by(|a, b| a.to_lowercase().cmp(&b.to_lowercase()));
+    themes
+}
+
 pub trait GetOptionValue {
     fn get_option_value(
         option_name: &str,
@@ -115,6 +138,7 @@ pub mod tests {
     use std::env;
     use std::fs::remove_file;
 
+    use crate::options::get::get_themes;
     use crate::tests::integration_test_utils::integration_test_utils;
 
     // TODO: the followig tests are collapsed into one since they all set the same env var and thus
@@ -275,4 +299,41 @@ pub mod tests {
 
         remove_file(git_config_path).unwrap();
     }
+
+    #[test]
+    fn test_get_themes_from_config() {
+        let git_config_contents = r#"
+[delta "dark-theme"]
+    max-line-distance = 0.6
+    dark = true
+
+[delta "light-theme"]
+    max-line-distance = 0.6
+    light = true
+
+[delta "light-and-dark-theme"]
+    max-line-distance = 0.6
+    light = true
+    dark = true
+
+[delta "not-a-theme"]
+    max-line-distance = 0.6
+"#;
+        let git_config_path = "delta__test_get_themes_git_config.gitconfig";
+
+        let git_config = Some(integration_test_utils::make_git_config(
+            git_config_contents.as_bytes(),
+            git_config_path,
+            false,
+        ));
+
+        let themes = get_themes(git_config);
+
+        assert_eq!(
+            themes,
+            ["dark-theme", "light-and-dark-theme", "light-theme",]
+        );
+
+        remove_file(git_config_path).unwrap();
+    }
 }
diff --git a/src/options/set.rs b/src/options/set.rs
index 354eeea6..e5c1edf0 100644
--- a/src/options/set.rs
+++ b/src/options/set.rs
@@ -169,6 +169,7 @@ pub fn set_options(
             plus_empty_line_marker_style,
             plus_non_emph_style,
             raw,
+            show_themes,
             side_by_side,
             tab_width,
             tokenization_regex,
diff --git a/src/options/theme.rs b/src/options/theme.rs
index ae831202..420c5be5 100644
--- a/src/options/theme.rs
+++ b/src/options/theme.rs
@@ -66,7 +66,7 @@ fn is_no_syntax_highlighting_syntax_theme_name(theme_name: &str) -> bool {
 ///    chosen for a light or dark terminal background. (`bat` has no equivalent.)
 ///
 /// Basically:
-/// 1. The theme is specified by the `--theme` option. If this isn't supplied then it is specified
+/// 1. The theme is specified by the `--syntax-theme` option. If this isn't supplied then it is specified
 ///    by the `BAT_THEME` environment variable.
 /// 2. Light vs dark mode is specified by the `--light` or `--dark` options. If these aren't
 ///    supplied then it is inferred from the chosen theme.