New option to map raw styles encountered in input

Unify handling of styles parsed from raw line and computed diff
styles. This enables syntax highlighting to be used in color-moved
sections.

Fixes #72

etc/examples/72-color-moved-2.diff

@@ -0,0 +1,8 @@
+diff --git a/file.py b/file.py
+index f07db74..3cb162d 100644
+--- a/file.py
++++ b/file.py
+@@ -1,2 +1,2 @@
+-class X: pass
+ class Y: pass
++class X: pass

etc/examples/72-color-moved-3.diff

@@ -0,0 +1,14 @@
+commit fffb6bf94087c432b6e2e29cab97bf1f8987c641
+Author: Dan Davison <dandavison7@gmail.com>
+Date:   Tue Nov 23 14:51:46 2021 -0500
+
+    DEBUG
+
+diff --git a/src/config.rs b/src/config.rs
+index efe6adb..9762222 100644
+--- a/src/config.rs
++++ b/src/config.rs
+@@ -400,6 +400,7 @@ fn make_blame_palette(blame_palette: Option<String>, is_light_mode: bool) -> Vec
++pub fn user_supplied_option(option: &str, arg_matches: &clap::ArgMatches) -> bool {
+@@ -416,29 +433,30 @@ fn make_styles_map(opt: &cli::Opt) -> Option<HashMap<style::AnsiTermStyleEqualit
+-pub fn user_supplied_option(option: &str, arg_matches: &clap::ArgMatches) -> bool {

src/cli.rs

@@ -429,6 +429,12 @@ pub struct Opt {
     /// (underline), 'ol' (overline), or the combination 'ul ol'.
     pub hunk_header_decoration_style: String,
 
+    #[structopt(long = "map-styles")]
+    /// A string specifying a mapping styles encountered in raw input to desired
+    /// output styles. An example is --map-styles='black cyan => white magenta,
+    /// red cyan => white blue'
+    pub map_styles: Option<String>,
+
     /// Format string for git blame commit metadata. Available placeholders are
     /// "{timestamp}", "{author}", and "{commit}".
     #[structopt(

src/config.rs

@@ -20,6 +20,7 @@ use crate::git_config::{GitConfig, GitConfigEntry};
 use crate::minusplus::MinusPlus;
 use crate::paint::BgFillMethod;
 use crate::parse_styles;
+use crate::style;
 use crate::style::Style;
 use crate::tests::TESTING;
 use crate::utils::bat::output::PagingMode;
@@ -105,6 +106,7 @@ pub struct Config {
     pub line_numbers_style_minusplus: MinusPlus<Style>,
     pub line_numbers_zero_style: Style,
     pub line_numbers: bool,
+    pub styles_map: Option<HashMap<style::AnsiTermStyleEqualityKey, Style>>,
     pub max_line_distance_for_naively_paired_lines: f64,
     pub max_line_distance: f64,
     pub max_line_length: usize,
@@ -157,6 +159,7 @@ impl Config {
 impl From<cli::Opt> for Config {
     fn from(opt: cli::Opt) -> Self {
         let styles = parse_styles::parse_styles(&opt);
+        let styles_map = make_styles_map(&opt);
 
         let max_line_distance_for_naively_paired_lines =
             env::get_env_var("DELTA_EXPERIMENTAL_MAX_LINE_DISTANCE_FOR_NAIVELY_PAIRED_LINES")
@@ -297,6 +300,7 @@ impl From<cli::Opt> for Config {
             ),
             line_numbers_zero_style: styles["line-numbers-zero-style"],
             line_buffer_size: opt.line_buffer_size,
+            styles_map,
             max_line_distance: opt.max_line_distance,
             max_line_distance_for_naively_paired_lines,
             max_line_length: match (opt.side_by_side, wrap_max_lines_plus1) {
@@ -396,6 +400,28 @@ fn make_blame_palette(blame_palette: Option<String>, is_light_mode: bool) -> Vec
     }
 }
 
+fn make_styles_map(opt: &cli::Opt) -> Option<HashMap<style::AnsiTermStyleEqualityKey, Style>> {
+    if let Some(styles_map_str) = &opt.map_styles {
+        let mut styles_map = HashMap::new();
+        for pair_str in styles_map_str.split(',') {
+            let mut style_strs = pair_str.split("=>").map(|s| s.trim());
+            if let (Some(from_str), Some(to_str)) = (style_strs.next(), style_strs.next()) {
+                let key = style::ansi_term_style_equality_key(
+                    Style::from_str(from_str, None, None, true, opt.git_config.as_ref())
+                        .ansi_term_style,
+                );
+                styles_map.insert(
+                    key,
+                    Style::from_str(to_str, None, None, true, opt.git_config.as_ref()),
+                );
+            }
+        }
+        Some(styles_map)
+    } else {
+        None
+    }
+}
+
 /// Did the user supply `option` on the command line?
 pub fn user_supplied_option(option: &str, arg_matches: &clap::ArgMatches) -> bool {
     arg_matches.occurrences_of(option) > 0

src/options/set.rs

@@ -157,6 +157,7 @@ pub fn set_options(
             inspect_raw_lines,
             keep_plus_minus_markers,
             line_buffer_size,
+            map_styles,
             max_line_distance,
             max_line_length,
             // Hack: minus-style must come before minus-*emph-style because the latter default