Handle git blame output

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"

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());
+    }
+}

src/cli.rs

@@ -419,6 +419,33 @@ pub struct Opt {
     /// (underline), 'ol' (overline), or the combination 'ul ol'.
     pub hunk_header_decoration_style: String,
 
+    /// 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>,
+
     /// The regular expression used to decide what a word is for the within-line highlight
     /// algorithm. For less fine-grained matching than the default try --word-diff-regex="\S+"
     /// --max-line-distance=1.0 (this is more similar to `git --word-diff`).

src/config.rs

@@ -21,11 +21,15 @@ 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,
     pub cwd_relative_to_repo_root: Option<String>,
     pub decorations_width: cli::Width,
+    pub default_language: Option<String>,
     pub diff_stat_align_width: usize,
     pub error_exit_code: i32,
     pub file_added_label: String,
@@ -201,11 +205,19 @@ 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,
             cwd_relative_to_repo_root: std::env::var("GIT_PREFIX").ok(),
             decorations_width: opt.computed.decorations_width,
+            default_language: opt.default_language,
             diff_stat_align_width: opt.diff_stat_align_width,
             error_exit_code: 2, // Use 2 for error because diff uses 0 and 1 for non-error.
             file_added_label,