feat: add autocompletion for diff-source command

helix-term/src/commands/typed.rs

@@ -3076,7 +3076,7 @@ pub const TYPABLE_COMMAND_LIST: &[TypableCommand] = &[
         aliases: &[],
         doc: "Set the diff source for the file. If no argument is provided, show the current source.",
         fun: diff_source,
-        signature: CommandSignature::none(),
+        signature: CommandSignature::all(completers::diff_source),
     },
     TypableCommand {
         name: "clear-register",

helix-term/src/ui/mod.rs

@@ -259,6 +259,7 @@ pub mod completers {
     use crate::ui::prompt::Completion;
     use helix_core::fuzzy::fuzzy_match;
     use helix_core::syntax::LanguageServerFeature;
+    use helix_vcs::DiffSource;
     use helix_view::document::SCRATCH_BUFFER_NAME;
     use helix_view::theme;
     use helix_view::{editor::Config, Editor};
@@ -523,4 +524,13 @@ pub mod completers {
             .map(|(name, _)| ((0..), name.into()))
             .collect()
     }
+
+    pub fn diff_source(_editor: &Editor, input: &str) -> Vec<Completion> {
+        let iter = DiffSource::all_values();
+
+        fuzzy_match(input, iter, false)
+            .into_iter()
+            .map(|(&name, _)| ((0..), name.into()))
+            .collect()
+    }
 }

helix-vcs/src/lib.rs

@@ -71,6 +71,24 @@ impl DiffSource {
             Self::Git => Some(git::get_current_head_name(file)),
         }
     }
+
+    /// Used to offer completion options for the `diff-source` command
+    pub fn all_values() -> &'static [&'static str] {
+        // To force a miscompilation and remember to add the value to the list
+        match Self::None {
+            Self::None => (),
+            Self::File => (),
+            Self::Git => (),
+        }
+
+        // Keep it sorted alphabetically
+        &[
+            "file",
+            #[cfg(feature = "git")]
+            "git",
+            "none",
+        ]
+    }
 }
 
 impl FromStr for DiffSource {
@@ -82,7 +100,7 @@ impl FromStr for DiffSource {
             "file" => Ok(Self::File),
             #[cfg(feature = "git")]
             "git" => Ok(Self::Git),
-            s => bail!("invalid diff source '{s}', pick one of 'none', 'file' or 'git'"),
+            s => bail!("invalid diff source '{s}'"),
         }
     }
 }
@@ -121,4 +139,12 @@ mod tests {
         #[cfg(feature = "git")]
         assert_eq!(DiffSource::Git.to_string(), "git");
     }
+
+    #[test]
+    fn test_diff_source_all_values() {
+        let all = DiffSource::all_values();
+        let mut all_sorted = all.to_vec();
+        all_sorted.sort_unstable();
+        assert_eq!(all, all_sorted);
+    }
 }