Handle blame output

Fixes #291, #426

10 files changed, 272 insertions, 9 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 2c115db1..dc970c6f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -145,8 +145,20 @@ version = "0.4.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "670ad68c9088c2a963aaa298cb369688cf3f9465ce5e2d4ca10e6e0098a1ce73"
 dependencies = [
+ "libc",
  "num-integer",
  "num-traits",
+ "time",
+ "winapi",
+]
+
+[[package]]
+name = "chrono-humanize"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2eddc119501d583fd930cb92144e605f44e0252c38dd89d9247fffa1993375cb"
+dependencies = [
+ "chrono",
 ]
 
 [[package]]
@@ -276,7 +288,7 @@ checksum = "8fc3cb4d91f53b50155bdcfd23f6a4c39ae1969c2ae85982b135750cccaf5fce"
 dependencies = [
  "cfg-if 1.0.0",
  "libc",
- "wasi",
+ "wasi 0.9.0+wasi-snapshot-preview1",
 ]
 
 [[package]]
@@ -289,6 +301,8 @@ dependencies = [
  "bitflags",
  "box_drawing",
  "bytelines",
+ "chrono",
+ "chrono-humanize",
  "console",
  "ctrlc",
  "dirs-next",
@@ -834,6 +848,17 @@ dependencies = [
 ]
 
 [[package]]
+name = "time"
+version = "0.1.44"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6db9e6914ab8b1ae1c260a4ae7a49b6c5611b40328a735b21862567685e73255"
+dependencies = [
+ "libc",
+ "wasi 0.10.0+wasi-snapshot-preview1",
+ "winapi",
+]
+
+[[package]]
 name = "tinyvec"
 version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -959,6 +984,12 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cccddf32554fecc6acb585f82a32a72e28b48f8c4c1883ddfeeeaa96f7d8e519"
 
 [[package]]
+name = "wasi"
+version = "0.10.0+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1a143597ca7c7793eff794def352d41792a93c481eb1042423ff7ff72ba2c31f"
+
+[[package]]
 name = "winapi"
 version = "0.3.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
diff --git a/Cargo.toml b/Cargo.toml
index 8a960b3e..8de22eb4 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -15,6 +15,8 @@ name = "delta"
 path = "src/main.rs"
 
 [dependencies]
+chrono = "0.4.19"
+chrono-humanize = "0.2.1"
 ansi_colours = "1.0.4"
 ansi_term = "0.12.1"
 atty = "0.2.14"
diff --git a/src/blame.rs b/src/blame.rs
new file mode 100644
index 00000000..bf15fdb1
--- /dev/null
+++ b/src/blame.rs
@@ -0,0 +1,122 @@
+use chrono::{DateTime, FixedOffset};
+use lazy_static::lazy_static;
+use regex::Regex;
+
+use crate::config;
+use crate::delta;
+use crate::format;
+
+#[derive(Debug)]
+pub struct BlameLine<'a> {
+    pub commit: &'a str,
+    pub author: &'a str,
+    pub time: DateTime<FixedOffset>,
+    pub line_number: usize,
+    pub code: &'a str,
+}
+
+// E.g.
+//ea82f2d0 (Dan Davison       2021-08-22 18:20:19 -0700 120)             let mut handled_line = self.handle_commit_meta_header_line()?
+
+lazy_static! {
+    static ref BLAME_LINE_REGEX: Regex = Regex::new(
+        r"(?x)
+^
+(
+    [0-9a-f]{8}    # commit hash
+)
+[\ ]
+\(                 # open (
+(
+    [^\ ].*[^\ ]   # author name
+)
+[\ ]+
+(                  # timestamp
+    [0-9]{4}-[0-9]{2}-[0-9]{2}\ [0-9]{2}:[0-9]{2}:[0-9]{2}\ [-+][0-9]{4}
+)
+[\ ]+
+(
+    [0-9]+        # line number
+)
+\)                # close )
+(
+    .*            # code, with leading space
+)
+$
+"
+    )
+    .unwrap();
+}
+
+pub fn parse_git_blame_line<'a>(line: &'a str, timestamp_format: &str) -> Option<BlameLine<'a>> {
+    if let Some(caps) = BLAME_LINE_REGEX.captures(line) {
+        let commit = caps.get(1).unwrap().as_str();
+        let author = caps.get(2).unwrap().as_str();
+        let timestamp = caps.get(3).unwrap().as_str();
+        if let Ok(time) = DateTime::parse_from_str(timestamp, timestamp_format) {
+            let line_number_str = caps.get(4).unwrap().as_str();
+            if let Ok(line_number) = line_number_str.parse::<usize>() {
+                let code = caps.get(5).unwrap().as_str();
+                Some(BlameLine {
+                    commit,
+                    author,
+                    time,
+                    line_number,
+                    code,
+                })
+            } else {
+                None
+            }
+        } else {
+            None
+        }
+    } else {
+        None
+    }
+}
+
+lazy_static! {
+    pub static ref BLAME_PLACEHOLDER_REGEX: Regex =
+        format::make_placeholder_regex(&["timestamp", "author", "commit"]);
+}
+
+pub fn format_blame_metadata(
+    format_data: &[format::FormatStringPlaceholderData],
+    blame: &BlameLine,
+    config: &config::Config,
+) -> String {
+    let mut s = String::new();
+    let mut suffix = "";
+    for placeholder in format_data {
+        s.push_str(placeholder.prefix);
+
+        let alignment_spec = placeholder.alignment_spec.unwrap_or("<");
+        let width = placeholder.width.unwrap_or(15);
+
+        let pad = |s| format::pad(s, width, alignment_spec);
+        match placeholder.placeholder {
+            Some("timestamp") => s.push_str(&pad(
+                &chrono_humanize::HumanTime::from(blame.time).to_string()
+            )),
+            Some("author") => s.push_str(&pad(blame.author)),
+            Some("commit") => s.push_str(&pad(&delta::format_raw_line(blame.commit, config))),
+            None => {}
+            Some(_) => unreachable!(),
+        }
+        suffix = placeholder.suffix;
+    }
+    s.push_str(suffix);
+    s
+}
+
+#[test]
+fn test_blame_line_regex() {
+    for line in &[
+        "ea82f2d0 (Dan Davison       2021-08-22 18:20:19 -0700 120)             let mut handled_line = self.handle_commit_meta_header_line()?",
+        "b2257cfa (Dan Davison  2020-07-18 15:34:43 -0400   1) use std::borrow::Cow;"
+    ] {
+        let caps = BLAME_LINE_REGEX.captures(line);
+        assert!(caps.is_some());
+        assert!(parse_git_blame_line(line, "%Y-%m-%d %H:%M:%S %z").is_some());
+    }
+}
diff --git a/src/cli.rs b/src/cli.rs
index cebbd282..6a335629 100644
--- a/src/cli.rs
+++ b/src/cli.rs
@@ -419,9 +419,30 @@ pub struct Opt {
     /// (underline), 'ol' (overline), or the combination 'ul ol'.
     pub hunk_header_decoration_style: String,
 
-    // Default language used for syntax highlighting when this cannot be
-    // inferred from a filename. It will typically make sense to set this in
-    // per-repository git config ().git/config)
+    /// Format string for git blame commit metadata. Available placeholders are
+    /// "{timestamp}", "{author}", and "{commit}".
+    #[structopt(
+        long = "blame-format",
+        default_value = "{timestamp:<15} {author:<15} {commit:<8} │ "
+    )]
+    pub blame_format: String,
+
+    /// Background colors used for git blame lines (space-separated string).
+    /// Lines added by the same commit are painted with the same color; colors
+    /// are recycled as needed.
+    #[structopt(long = "blame-palette")]
+    pub blame_palette: Option<String>,
+
+    /// Format of `git blame` timestamp in raw git output received by delta.
+    #[structopt(
+        long = "blame-timestamp-format",
+        default_value = "%Y-%m-%d %H:%M:%S %z"
+    )]
+    pub blame_timestamp_format: String,
+
+    /// Default language used for syntax highlighting when this cannot be
+    /// inferred from a filename. It will typically make sense to set this in
+    /// per-repository git config ().git/config)
     #[structopt(long = "default-language")]
     pub default_language: Option<String>,
 
diff --git a/src/config.rs b/src/config.rs
index d45c2124..71580ddb 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -21,6 +21,9 @@ use crate::style::{self, Style};
 pub struct Config {
     pub available_terminal_width: usize,
     pub background_color_extends_to_terminal_width: bool,
+    pub blame_format: String,
+    pub blame_palette: Option<Vec<String>>,
+    pub blame_timestamp_format: String,
     pub commit_style: Style,
     pub color_only: bool,
     pub commit_regex: Regex,
@@ -202,6 +205,13 @@ impl From<cli::Opt> for Config {
             background_color_extends_to_terminal_width: opt
                 .computed
                 .background_color_extends_to_terminal_width,
+            blame_format: opt.blame_format,
+            blame_palette: opt.blame_palette.map(|s| {
+                s.split_whitespace()
+                    .map(|s| s.to_owned())
+                    .collect::<Vec<String>>()
+            }),
+            blame_timestamp_format: opt.blame_timestamp_format,
             commit_style,
             color_only: opt.color_only,
             commit_regex,
diff --git a/src/delta.rs b/src/delta.rs
index bb8c1afc..61dd475c 100644
--- a/src/delta.rs
+++ b/src/delta.rs
@@ -1,4 +1,5 @@
 use std::borrow::Cow;
+use std::collections::HashMap;
 use std::io::BufRead;
 use std::io::Write;
 
@@ -6,7 +7,9 @@ use bytelines::ByteLines;
 use unicode_segmentation::UnicodeSegmentation;
 
 use crate::ansi;
+use crate::blame;
 use crate::cli;
+use crate::color;
 use crate::config::Config;
 use crate::draw;
 use crate::features;
@@ -14,7 +17,7 @@ use crate::format;
 use crate::hunk_header;
 use crate::paint::Painter;
 use crate::parse;
-use crate::style::{self, DecorationStyle};
+use crate::style::{self, DecorationStyle, Style};
 
 #[derive(Clone, Debug, PartialEq)]
 pub enum State {
@@ -26,6 +29,7 @@ pub enum State {
     HunkPlus(Option<String>), // In hunk; added line (raw_line)
     SubmoduleLog, // In a submodule section, with gitconfig diff.submodule = log
     SubmoduleShort(String), // In a submodule section, with gitconfig diff.submodule = short
+    Blame(String), // In a line of `git blame` output.
     Unknown,
 }
 
@@ -77,6 +81,7 @@ struct StateMachine<'a> {
     // avoid emitting the file meta header line twice (#245).
     current_file_pair: Option<(String, String)>,
     handled_file_meta_header_line_file_pair: Option<(String, String)>,
+    blame_commit_colors: HashMap<String, String>,
 }
 
 pub fn delta<I>(lines: ByteLines<I>, writer: &mut dyn Write, config: &Config) -> std::io::Result<()>
@@ -102,6 +107,7 @@ impl<'a> StateMachine<'a> {
             handled_file_meta_header_line_file_pair: None,
             painter: Painter::new(writer, config),
             config,
+            blame_commit_colors: HashMap::new(),
         }
     }
 
@@ -126,7 +132,8 @@ impl<'a> StateMachine<'a> {
                 || self.handle_additional_file_meta_cases()?
                 || self.handle_submodule_log_line()?
                 || self.handle_submodule_short_line()?
-                || self.handle_hunk_line()?;
+                || self.handle_hunk_line()?
+                || self.handle_blame_line()?;
 
             if self.state == State::FileMeta && self.should_handle() && !self.config.color_only {
                 // Skip file metadata lines unless a raw diff style has been requested.
@@ -463,6 +470,70 @@ impl<'a> StateMachine<'a> {
         Ok(true)
     }
 
+    /// If this is a line of git blame output then render it accordingly. If
+    /// this is the first blame line, then set the syntax-highlighter language
+    /// according to delta.default-language.
+    fn handle_blame_line(&mut self) -> std::io::Result<bool> {
+        let mut handled_line = false;
+        self.painter.emit()?;
+        if matches!(self.state, State::Unknown | State::Blame(_)) {
+            if let Some(blame) =
+                blame::parse_git_blame_line(&self.line, &self.config.blame_timestamp_format)
+            {
+                // Determine color for this line
+                let color = if let Some(color) = self.blame_commit_colors.get(blame.commit) {
+                    color
+                } else {
+                    let n_commits = self.blame_commit_colors.len();
+                    let n_colors = self.config.blame_palette.as_ref().map(|v| v.len()).unwrap();
+                    let new_color = self
+                        .config
+                        .blame_palette
+                        .as_ref()
+                        .map(|v| &v[(n_commits + 1) % n_colors])
+                        .unwrap();
+                    self.blame_commit_colors
+                        .insert(blame.commit.to_owned(), new_color.to_owned());
+                    new_color
+                };
+                let mut style = Style::from_colors(None, color::parse_color(color, true));
+                style.is_syntax_highlighted = true;
+
+                // Construct commit metadata, paint, and emit
+                let format_data = format::parse_line_number_format(
+                    &self.config.blame_format,
+                    &*blame::BLAME_PLACEHOLDER_REGEX,
+                );
+                write!(
+                    self.painter.writer,
+                    "{}",
+                    style.paint(blame::format_blame_metadata(
+                        &format_data,
+                        &blame,
+                        self.config
+                    ))
+                )?;
+
+                // Emit syntax-highlighted code
+                if matches!(self.state, State::Unknown) {
+                    if let Some(lang) = self.config.default_language.as_ref() {
+                        self.painter.set_syntax(Some(lang));
+                        self.painter.set_highlighter();
+                    }
+                    self.state = State::Blame(blame.commit.to_owned());
+                }
+                self.painter.syntax_highlight_and_paint_line(
+                    blame.code,
+                    style,
+                    self.state.clone(),
+                    true,
+                );
+                handled_line = true
+            }
+        }
+        Ok(handled_line)
+    }
+
     fn _handle_additional_cases(&mut self, to_state: State) -> std::io::Result<bool> {
         let mut handled_line = false;
 
@@ -635,7 +706,7 @@ impl<'a> StateMachine<'a> {
 
 /// If output is going to a tty, emit hyperlinks if requested.
 // Although raw output should basically be emitted unaltered, we do this.
-fn format_raw_line<'a>(line: &'a str, config: &Config) -> Cow<'a, str> {
+pub fn format_raw_line<'a>(line: &'a str, config: &Config) -> Cow<'a, str> {
     if config.hyperlinks && atty::is(atty::Stream::Stdout) {
         features::hyperlinks::format_commit_line_with_osc8_commit_hyperlink(line, config)
     } else {
diff --git a/src/features/hyperlinks.rs b/src/features/hyperlinks.rs
index 2d3ad3b0..6637734c 100644
--- a/src/features/hyperlinks.rs
+++ b/src/features/hyperlinks.rs
@@ -88,7 +88,7 @@ fn format_osc8_hyperlink(url: &str, text: &str) -> String {
 }
 
 lazy_static! {
-    static ref COMMIT_LINE_REGEX: Regex = Regex::new("(.* )([0-9a-f]{40})(.*)").unwrap();
+    static ref COMMIT_LINE_REGEX: Regex = Regex::new("(.* )?([0-9a-f]{8,40})(.*)").unwrap();
 }
 
 fn format_commit_line_captures_with_osc8_commit_hyperlink(
@@ -100,7 +100,7 @@ fn format_commit_line_captures_with_osc8_commit_hyperlink(
         "{prefix}{osc}8;;{url}{st}{commit}{osc}8;;{st}{suffix}",
         url = format_github_commit_url(commit, github_repo),
         commit = commit,
-        prefix = captures.get(1).unwrap().as_str(),
+        prefix = captures.get(1).map(|m| m.as_str()).unwrap_or(""),
         suffix = captures.get(3).unwrap().as_str(),
         osc = "\x1b]",
         st = "\x1b\\"
diff --git a/src/main.rs b/src/main.rs
index ccf82661..a248c847 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -7,6 +7,7 @@ mod align;
 mod ansi;
 #[cfg(not(tarpaulin_include))]
 mod bat_utils;
+mod blame;
 mod cli;
 mod color;
 mod config;
diff --git a/src/options/set.rs b/src/options/set.rs
index 34d87bdf..ab888517 100644
--- a/src/options/set.rs
+++ b/src/options/set.rs
@@ -121,6 +121,9 @@ pub fn set_options(
 
     set_options!(
         [
+            blame_format,
+            blame_palette,
+            blame_timestamp_format,
             color_only,
             commit_decoration_style,
             commit_regex,
diff --git a/src/paint.rs b/src/paint.rs
index f807146a..a575d3bf 100644
--- a/src/paint.rs
+++ b/src/paint.rs
@@ -358,6 +358,7 @@ impl<'a> Painter<'a> {
                     (config.plus_style, config.plus_non_emph_style)
                 }
             }
+            State::Blame(_) => (diff_sections[0].0, diff_sections[0].0),
             _ => (config.null_style, config.null_style),
         };
         let fill_style = if style_sections_contain_more_than_one_style(diff_sections) {
@@ -494,6 +495,7 @@ impl<'a> Painter<'a> {
             }
             State::HunkHeader(_, _) => true,
             State::HunkMinus(Some(_)) | State::HunkPlus(Some(_)) => false,
+            State::Blame(_) => true,
             _ => panic!(
                 "should_compute_syntax_highlighting is undefined for state {:?}",
                 state