Add inspect-raw-lines {true,false} option

Fixes #72

README.md

@@ -14,6 +14,7 @@ Code evolves, and studying diffs is a fundamental mode of work. Delta aims to ma
 - Line numbering
 - `diff-highlight` and `diff-so-fancy` emulation modes
 - Stylable box/line decorations to draw attention to commit, file and hunk header sections.
+- Support for Git's `--color-moved` feature.
 - Code can be copied directly from the diff (`-/+` markers are removed by default).
 - `n` and `N` keybindings to move between files in large diffs, and between diffs in `log -p` views (`--navigate`)
 
@@ -59,6 +60,7 @@ Contents
    * [Side-by-side view](#side-by-side-view)
    * [Custom features](#custom-features)
    * [diff-highlight and diff-so-fancy emulation](#diff-highlight-and-diff-so-fancy-emulation)
+   * [--color-moved support](#--color-moved-support)
    * [Navigation keybindings for large diffs](#navigation-keybindings-for-large-diffs)
    * [24 bit color (truecolor)](#24-bit-color-truecolor)
    * [Using Delta on Windows](#using-delta-on-windows)
@@ -356,6 +358,28 @@ You may want to know which delta configuration values the emulation mode has sel
 
 The within-line highlighting rules employed by diff-highlight (and therefore by diff-so-fancy) are deliberately simpler than Delta's Levenshtein-type edit inference algorithm (see discussion in the [diff-highlight README](https://github.com/git/git/tree/master/contrib/diff-highlight)). diff-highlight's rules could be added to delta as an alternative highlighting algorithm, but that hasn't been done yet.
 
+### `--color-moved` support
+
+[_**Unreleased feature**: available now if you build Delta from source, and will be included in the next Delta release. See [#72](https://github.com/dandavison/delta/issues/2)._]
+
+Recent versions of Git are able to detect moved blocks of code and style them differently from the usual removed/added lines. If you have activated this feature in Git, then Delta will automatically detect such differently-styled lines, and display them unchanged, i.e. with the raw colors it receives from Git.
+
+To activate the Git feature, use
+
+```gitconfig
+[diff]
+    colorMoved = default
+```
+
+and see the [Git documentation](https://git-scm.com/docs/git-diff#Documentation/git-diff.txt---color-movedltmodegt) for the other possible values and associated color configuration.
+
+In order to support this feature, Delta has to look at the raw colors it receives in a line from Git, and use them to judge whether it is a typical removed/added line, or a specially-colored moved line. This should just work. However, if it causes problems, the behavior can be disabled using
+
+```gitconfig
+[delta]
+    inspect-raw-lines = false
+```
+
 ### Navigation keybindings for large diffs
 
 Use the `navigate` feature to activate navigation keybindings. In this mode, pressing `n` will jump forward to the next file in the diff, and `N` will jump backwards. If you are viewing multiple commits (e.g. via `git log -p`) then navigation will also visit commit boundaries.

src/cli.rs

@@ -464,6 +464,12 @@ pub struct Opt {
     #[structopt(long = "24-bit-color", default_value = "auto")]
     pub true_color: String,
 
+    /// Whether to examine ANSI color escape sequences in raw lines received from Git and handle
+    /// lines colored in certain ways specially. This is on by default: it is how Delta supports
+    /// Git's --color-moved feature. Set this to "false" to disable this behavior.
+    #[structopt(long = "inspect-raw-lines", default_value = "true")]
+    pub inspect_raw_lines: String,
+
     /// Whether to use a pager when displaying output. Options are: auto, always, and never. The
     /// default pager is `less`: this can be altered by setting the environment variables BAT_PAGER
     /// or PAGER (BAT_PAGER has priority).
@@ -549,6 +555,7 @@ pub struct Opt {
 
 #[derive(Default, Clone, Debug)]
 pub struct ComputedValues {
+    pub inspect_raw_lines: InspectRawLines,
     pub is_light_mode: bool,
     pub syntax_set: SyntaxSet,
     pub syntax_theme: Option<SyntaxTheme>,
@@ -572,6 +579,18 @@ impl Default for Width {
     }
 }
 
+#[derive(Clone, Debug)]
+pub enum InspectRawLines {
+    True,
+    False,
+}
+
+impl Default for InspectRawLines {
+    fn default() -> Self {
+        InspectRawLines::False
+    }
+}
+
 impl Default for PagingMode {
     fn default() -> Self {
         PagingMode::Never

src/config.rs

@@ -31,6 +31,7 @@ pub struct Config {
     pub hunk_header_style: Style,
     pub hyperlinks: bool,
     pub hyperlinks_file_link_format: String,
+    pub inspect_raw_lines: cli::InspectRawLines,
     pub keep_plus_minus_markers: bool,
     pub line_numbers: bool,
     pub line_numbers_left_format: String,
@@ -156,6 +157,7 @@ impl From<cli::Opt> for Config {
             hunk_header_style,
             hyperlinks: opt.hyperlinks,
             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_left_format: opt.line_numbers_left_format,

src/delta.rs

@@ -6,6 +6,7 @@ use bytelines::ByteLines;
 use console::strip_ansi_codes;
 use unicode_segmentation::UnicodeSegmentation;
 
+use crate::cli;
 use crate::config::Config;
 use crate::draw;
 use crate::features;
@@ -502,27 +503,33 @@ fn handle_hunk_line(
             if let State::HunkPlus(_) = state {
                 painter.paint_buffered_minus_and_plus_lines();
             }
-            let state = if style::line_has_style_other_than(
-                raw_line,
-                [*style::GIT_DEFAULT_MINUS_STYLE, config.git_minus_style].iter(),
-            ) {
-                State::HunkMinus(Some(painter.prepare_raw_line(raw_line)))
-            } else {
-                State::HunkMinus(None)
+            let state = match config.inspect_raw_lines {
+                cli::InspectRawLines::True
+                    if style::line_has_style_other_than(
+                        raw_line,
+                        [*style::GIT_DEFAULT_MINUS_STYLE, config.git_minus_style].iter(),
+                    ) =>
+                {
+                    State::HunkMinus(Some(painter.prepare_raw_line(raw_line)))
+                }
+                _ => State::HunkMinus(None),
             };
             painter
                 .minus_lines
                 .push((painter.prepare(&line, true), state.clone()));
             state
         }
         Some('+') => {
-            let state = if style::line_has_style_other_than(
-                raw_line,
-                [*style::GIT_DEFAULT_PLUS_STYLE, config.git_plus_style].iter(),
-            ) {
-                State::HunkPlus(Some(painter.prepare_raw_line(raw_line)))
-            } else {
-                State::HunkPlus(None)
+            let state = match config.inspect_raw_lines {
+                cli::InspectRawLines::True
+                    if style::line_has_style_other_than(
+                        raw_line,
+                        [*style::GIT_DEFAULT_PLUS_STYLE, config.git_plus_style].iter(),
+                    ) =>
+                {
+                    State::HunkPlus(Some(painter.prepare_raw_line(raw_line)))
+                }
+                _ => State::HunkPlus(None),
             };
             painter
                 .plus_lines

src/main.rs

@@ -181,6 +181,7 @@ fn show_config(config: &config::Config) {
     file-modified-label           = {file_modified_label}
     file-removed-label            = {file_removed_label}
     file-renamed-label            = {file_renamed_label}
+    inspect-raw-lines             = {inspect_raw_lines}
     keep-plus-minus-markers       = {keep_plus_minus_markers}
     max-line-distance             = {max_line_distance}
     navigate                      = {navigate}
@@ -194,6 +195,10 @@ fn show_config(config: &config::Config) {
         file_modified_label = format_option_value(&config.file_modified_label),
         file_removed_label = format_option_value(&config.file_removed_label),
         file_renamed_label = format_option_value(&config.file_renamed_label),
+        inspect_raw_lines = match config.inspect_raw_lines {
+            cli::InspectRawLines::True => "true",
+            cli::InspectRawLines::False => "false",
+        },
         keep_plus_minus_markers = config.keep_plus_minus_markers,
         max_line_distance = config.max_line_distance,
         navigate = config.navigate,

src/options/set.rs

@@ -1,5 +1,6 @@
 use std::collections::{HashMap, HashSet, VecDeque};
 use std::process;
+use std::result::Result;
 use std::str::FromStr;
 
 use console::Term;
@@ -10,6 +11,7 @@ use crate::bat::output::PagingMode;
 use crate::cli;
 use crate::config;
 use crate::env;
+use crate::errors::*;
 use crate::features;
 use crate::git_config;
 use crate::git_config_entry::{self, GitConfigEntry};
@@ -128,6 +130,7 @@ pub fn set_options(
             hunk_header_style,
             hyperlinks,
             hyperlinks_file_link_format,
+            inspect_raw_lines,
             keep_plus_minus_markers,
             max_line_distance,
             // Hack: minus-style must come before minus-*emph-style because the latter default
@@ -170,6 +173,8 @@ pub fn set_options(
         true
     );
 
+    opt.computed.inspect_raw_lines =
+        cli::InspectRawLines::from_str(&opt.inspect_raw_lines).unwrap();
     opt.computed.paging_mode = parse_paging_mode(&opt.paging_mode);
 }
 
@@ -463,6 +468,23 @@ fn is_truecolor_terminal() -> bool {
         .unwrap_or(false)
 }
 
+impl FromStr for cli::InspectRawLines {
+    type Err = Error;
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s.to_lowercase().as_str() {
+            "true" => Ok(Self::True),
+            "false" => Ok(Self::False),
+            _ => {
+                eprintln!(
+                    r#"Invalid value for inspect-raw-lines option: {}. Valid values are "true", and "false"."#,
+                    s
+                );
+                process::exit(1);
+            }
+        }
+    }
+}
+
 fn parse_paging_mode(paging_mode_string: &str) -> PagingMode {
     match paging_mode_string.to_lowercase().as_str() {
         "always" => PagingMode::Always,