Truncate long lines (#290)

Fixes #154, #288

src/cli.rs

@@ -443,6 +443,12 @@ pub struct Opt {
     /// Text to display in front of a renamed file path.
     pub file_renamed_label: String,
 
+    #[structopt(long = "max-line-length", default_value = "512")]
+    /// Truncate lines longer than this. To prevent any truncation, set to zero. Note that
+    /// syntax-highlighting very long lines (e.g. minified .js) will be very slow if they are not
+    /// truncated.
+    pub max_line_length: usize,
+
     /// The width of underline/overline decorations. Use --width=variable to extend decorations and
     /// background colors to the end of the text only. Otherwise background colors extend to the
     /// full terminal width.

src/config.rs

@@ -44,6 +44,7 @@ pub struct Config {
     pub max_buffered_lines: usize,
     pub max_line_distance: f64,
     pub max_line_distance_for_naively_paired_lines: f64,
+    pub max_line_length: usize,
     pub minus_emph_style: Style,
     pub minus_empty_line_marker_style: Style,
     pub minus_file: Option<PathBuf>,
@@ -170,6 +171,7 @@ impl From<cli::Opt> for Config {
             max_buffered_lines: 32,
             max_line_distance: opt.max_line_distance,
             max_line_distance_for_naively_paired_lines,
+            max_line_length: opt.max_line_length,
             minus_emph_style,
             minus_empty_line_marker_style,
             minus_file: opt.minus_file.map(|s| s.clone()),

src/delta.rs

@@ -78,6 +78,11 @@ where
 
     while let Some(Ok(raw_line_bytes)) = lines.next() {
         let raw_line = String::from_utf8_lossy(&raw_line_bytes);
+        let raw_line = if config.max_line_length > 0 && raw_line.len() > config.max_line_length {
+            ansi::truncate_str(&raw_line, config.max_line_length, &config.truncation_symbol)
+        } else {
+            raw_line
+        };
         let line = ansi::strip_ansi_codes(&raw_line).to_string();
         if source == Source::Unknown {
             source = detect_source(&line);

src/options/set.rs

@@ -140,6 +140,7 @@ pub fn set_options(
             inspect_raw_lines,
             keep_plus_minus_markers,
             max_line_distance,
+            max_line_length,
             // Hack: minus-style must come before minus-*emph-style because the latter default
             // dynamically to the value of the former.
             minus_style,

tests/test_raw_output_matches_git_on_full_repo_history

@@ -1,5 +1,5 @@
 #!/bin/bash
-DELTA="./target/release/delta --no-gitconfig --raw"
+DELTA="./target/release/delta --no-gitconfig --raw --max-line-length 0"
 ANSIFILTER="./etc/bin/ansifilter"
 GIT_ARGS="log --patch --stat --numstat"
 diff -u <(git $GIT_ARGS | $ANSIFILTER) <(git $GIT_ARGS | $DELTA | $ANSIFILTER)