Interpret `line-numbers = false` in gitconfig as no line numbers at all (#296)

Fixes #292

5 files changed, 59 insertions, 3 deletions

diff --git a/src/cli.rs b/src/cli.rs
index b2e27886..6c29f9dc 100644
--- a/src/cli.rs
+++ b/src/cli.rs
@@ -566,6 +566,7 @@ pub struct ComputedValues {
     pub decorations_width: Width,
     pub inspect_raw_lines: InspectRawLines,
     pub is_light_mode: bool,
+    pub line_numbers_mode: LineNumbersMode,
     pub paging_mode: PagingMode,
     pub syntax_dummy_theme: SyntaxTheme,
     pub syntax_set: SyntaxSet,
@@ -597,6 +598,19 @@ impl Default for InspectRawLines {
     }
 }
 
+#[derive(Clone, Debug, PartialEq)]
+pub enum LineNumbersMode {
+    None,
+    First,
+    Full,
+}
+
+impl Default for LineNumbersMode {
+    fn default() -> Self {
+        LineNumbersMode::First
+    }
+}
+
 impl Default for PagingMode {
     fn default() -> Self {
         PagingMode::Never
diff --git a/src/config.rs b/src/config.rs
index 91887d3b..b383784a 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -40,6 +40,7 @@ pub struct Config {
     pub line_numbers_plus_style: Style,
     pub line_numbers_right_format: String,
     pub line_numbers_right_style: Style,
+    pub line_numbers_show_first_line_number: bool,
     pub line_numbers_zero_style: Style,
     pub max_buffered_lines: usize,
     pub max_line_distance: f64,
@@ -160,13 +161,20 @@ impl From<cli::Opt> for Config {
             hyperlinks_file_link_format: opt.hyperlinks_file_link_format,
             inspect_raw_lines: opt.computed.inspect_raw_lines,
             keep_plus_minus_markers: opt.keep_plus_minus_markers,
-            line_numbers: opt.line_numbers,
+            line_numbers: match opt.computed.line_numbers_mode {
+                cli::LineNumbersMode::Full => true,
+                _ => false,
+            },
             line_numbers_left_format: opt.line_numbers_left_format,
             line_numbers_left_style,
             line_numbers_minus_style,
             line_numbers_plus_style,
             line_numbers_right_format: opt.line_numbers_right_format,
             line_numbers_right_style,
+            line_numbers_show_first_line_number: match opt.computed.line_numbers_mode {
+                cli::LineNumbersMode::First => true,
+                _ => false,
+            },
             line_numbers_zero_style,
             max_buffered_lines: 32,
             max_line_distance: opt.max_line_distance,
diff --git a/src/delta.rs b/src/delta.rs
index d256e77a..9c411d8e 100644
--- a/src/delta.rs
+++ b/src/delta.rs
@@ -476,7 +476,7 @@ fn handle_hunk_header_line(
         painter
             .line_numbers_data
             .initialize_hunk(line_numbers, plus_file.to_string());
-    } else if !config.hunk_header_style.is_raw {
+    } else if config.line_numbers_show_first_line_number && !config.hunk_header_style.is_raw {
         let plus_line_number = line_numbers[line_numbers.len() - 1].0;
         let formatted_plus_line_number = if config.hyperlinks {
             features::hyperlinks::format_osc8_file_hyperlink(
diff --git a/src/options/option_value.rs b/src/options/option_value.rs
index cbe5b383..d569f676 100644
--- a/src/options/option_value.rs
+++ b/src/options/option_value.rs
@@ -55,6 +55,13 @@ impl From<OptionValue> for Option<String> {
     fn from(value: OptionValue) -> Self {
         match value {
             OptionValue::OptionString(value) => value,
+            // HACK: See the comment in options::set::compute_line_numbers_mode(). That function
+            // deliberately reads what is normally a boolean value ('line-numbers') as a string.
+            // However options::get::get_option_value() can fall through to obtaining the value
+            // from builtin_features, in which case an OptionValue::Boolean will be encountered.
+            // See the comment in options::set::compute_line_numbers_mode() and docstring of
+            // options::get::get_option_value().
+            OptionValue::Boolean(_) => None,
             _ => delta_unreachable("Error converting OptionValue to Option<String>."),
         }
     }
diff --git a/src/options/set.rs b/src/options/set.rs
index 150246c9..b8ea10a7 100644
--- a/src/options/set.rs
+++ b/src/options/set.rs
@@ -16,7 +16,7 @@ use crate::features;
 use crate::git_config;
 use crate::git_config_entry::{self, GitConfigEntry};
 use crate::options::option_value::{OptionValue, ProvenancedOptionValue};
-use crate::options::theme;
+use crate::options::{self, theme};
 
 macro_rules! set_options {
 	([$( $field_ident:ident ),* ],
@@ -183,6 +183,8 @@ pub fn set_options(
 
     opt.computed.inspect_raw_lines =
         cli::InspectRawLines::from_str(&opt.inspect_raw_lines).unwrap();
+    opt.computed.line_numbers_mode =
+        compute_line_numbers_mode(opt, &builtin_features, git_config, &option_names);
     opt.computed.paging_mode = parse_paging_mode(&opt.paging_mode);
 
     // --color-only is used for interactive.diffFilter (git add -p) and side-by-side cannot be used
@@ -192,6 +194,31 @@ pub fn set_options(
     }
 }
 
+fn compute_line_numbers_mode(
+    opt: &cli::Opt,
+    builtin_features: &HashMap<String, features::BuiltinFeature>,
+    git_config: &mut Option<git_config::GitConfig>,
+    option_names: &HashMap<&str, &str>,
+) -> cli::LineNumbersMode {
+    // line-numbers is in general treated as a boolean value. We read it as a string here in order
+    // to interpret an explicit "false" (as opposed to merely absence) as meaning "Do not show any
+    // line numbers; not even the first line number of the hunk".
+    let line_numbers_string_value: Option<Option<String>> = options::get::get_option_value(
+        option_names["line-numbers"],
+        builtin_features,
+        opt,
+        git_config,
+    );
+    match (
+        line_numbers_string_value.as_ref().map(|val| val.as_deref()),
+        opt.line_numbers,
+    ) {
+        (Some(Some("false")), _) => cli::LineNumbersMode::None,
+        (_, true) => cli::LineNumbersMode::Full,
+        (_, false) => cli::LineNumbersMode::First,
+    }
+}
+
 #[allow(non_snake_case)]
 fn set__light__dark__syntax_theme__options(
     opt: &mut cli::Opt,