Replace gix with configurable libgit2 diffs

src/config.rs

@@ -1,5 +1,6 @@
 use serde::{Deserialize, Serialize};
 use serde_norway::{Mapping, Value};
+use std::fmt;
 use std::fs;
 use std::path::Path;
 
@@ -19,6 +20,7 @@ pub struct Config {
     pub endpoint: EndpointConfig,
     pub generation: GenerationPreferences,
     pub runtime: RuntimePreferences,
+    pub git: GitConfig,
     pub interface: InterfaceConfig,
 }
 
@@ -32,11 +34,89 @@ impl Default for Config {
             endpoint: EndpointConfig::default(),
             generation: GenerationPreferences::default(),
             runtime: RuntimePreferences::default(),
+            git: GitConfig::default(),
             interface: InterfaceConfig::default(),
         }
     }
 }
 
+pub const GIT_DIFF_ALGORITHMS: [GitDiffAlgorithm; 3] = [
+    GitDiffAlgorithm::Default,
+    GitDiffAlgorithm::Patience,
+    GitDiffAlgorithm::Minimal,
+];
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, Eq, PartialEq, Serialize)]
+#[serde(rename_all = "kebab-case")]
+pub enum GitDiffAlgorithm {
+    #[default]
+    Default,
+    Patience,
+    Minimal,
+}
+
+impl fmt::Display for GitDiffAlgorithm {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        formatter.write_str(match self {
+            Self::Default => "Default (Myers)",
+            Self::Patience => "Patience",
+            Self::Minimal => "Minimal",
+        })
+    }
+}
+
+pub const GIT_DIFF_WHITESPACE_MODES: [GitDiffWhitespace; 4] = [
+    GitDiffWhitespace::ShowAll,
+    GitDiffWhitespace::IgnoreAll,
+    GitDiffWhitespace::IgnoreChanges,
+    GitDiffWhitespace::IgnoreEndOfLine,
+];
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, Eq, PartialEq, Serialize)]
+#[serde(rename_all = "kebab-case")]
+pub enum GitDiffWhitespace {
+    #[default]
+    ShowAll,
+    IgnoreAll,
+    IgnoreChanges,
+    IgnoreEndOfLine,
+}
+
+impl fmt::Display for GitDiffWhitespace {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        formatter.write_str(match self {
+            Self::ShowAll => "Show all changes",
+            Self::IgnoreAll => "Ignore all whitespace",
+            Self::IgnoreChanges => "Ignore whitespace amount",
+            Self::IgnoreEndOfLine => "Ignore end-of-line whitespace",
+        })
+    }
+}
+
+#[derive(Clone, Debug, Deserialize, Eq, PartialEq, Serialize)]
+#[serde(default, deny_unknown_fields)]
+pub struct GitConfig {
+    pub diff_algorithm: GitDiffAlgorithm,
+    pub context_lines: u32,
+    pub interhunk_lines: u32,
+    pub indent_heuristic: bool,
+    pub whitespace: GitDiffWhitespace,
+    pub ignore_blank_lines: bool,
+}
+
+impl Default for GitConfig {
+    fn default() -> Self {
+        Self {
+            diff_algorithm: GitDiffAlgorithm::Default,
+            context_lines: 3,
+            interhunk_lines: 0,
+            indent_heuristic: false,
+            whitespace: GitDiffWhitespace::ShowAll,
+            ignore_blank_lines: false,
+        }
+    }
+}
+
 #[derive(Clone, Debug, Default, Deserialize, Eq, PartialEq, Serialize)]
 #[serde(default, deny_unknown_fields)]
 pub struct DevBrainConfig {
@@ -201,6 +281,12 @@ mod tests {
                 },
                 ..RuntimePreferences::default()
             },
+            git: GitConfig {
+                diff_algorithm: GitDiffAlgorithm::Patience,
+                context_lines: 5,
+                whitespace: GitDiffWhitespace::IgnoreEndOfLine,
+                ..GitConfig::default()
+            },
             ..Config::default()
         };
         config.save(&path).unwrap();
@@ -210,7 +296,8 @@ mod tests {
             text,
             "model: glm-5.2\na2ui_enabled: false\n\
              generation:\n  context_tokens: 65536\n  reasoning_mode: none\n\
-             runtime:\n  ssd:\n    enabled: true\n    cache: 64GB\n"
+             runtime:\n  ssd:\n    enabled: true\n    cache: 64GB\n\
+             git:\n  diff_algorithm: patience\n  context_lines: 5\n  whitespace: ignore-end-of-line\n"
         );
         assert_eq!(Config::load(&path).unwrap(), config);
         fs::remove_dir_all(&directory).unwrap();