Handle grep output

- Handle standard filepath:code and filepath:line_number:code output
  as produced by `git grep`, `rg -H`, `grep -H`, etc (with -n for line
  numbers).

- Retain the match highlighting as produced by the grep tool, and
  expose it in delta's color output styled with grep-match-style.
  (Note that --color=always is needed to retain the color if piping
  into delta, but not for `git grep` when delta is configured as git's
  pager)

- Special handling of -p, and -W options of `git grep`: these display
  the function context in which the matches occur.

- `navigate` keybindings jump between match function contexts under
  `git grep -p` and between matching lines under `git grep -W`.

Thanks @zachriggle for the proposal.
Fixes #769

Cargo.toml

@@ -31,6 +31,8 @@ itertools = "0.10.1"
 lazy_static = "1.4"
 pathdiff = "0.2.1"
 regex = "1.4.6"
+serde = { version = "1.0.118", features = ["derive"] }
+serde_json = "1.0.70"
 shell-words = "1.0.0"
 smol_str = "0.1.18"
 structopt = "0.3.25"

README.md

@@ -23,6 +23,7 @@
     show = delta
     log = delta
     blame = delta
+    grep = delta
     reflog = delta
 
 [interactive]
@@ -64,6 +65,7 @@ Code evolves, and we all spend time studying diffs. Delta aims to make this both
   - [Choosing colors (styles)](#choosing-colors-styles)
   - [Line numbers](#line-numbers)
   - [Side-by-side view](#side-by-side-view)
+  - [Grep](#grep)
   - ["Features": named groups of settings](#features-named-groups-of-settings)
   - [Custom themes](#custom-themes)
   - [diff-highlight and diff-so-fancy emulation](#diff-highlight-and-diff-so-fancy-emulation)
@@ -151,6 +153,7 @@ Here's what `git show` can look like with git configured to use delta:
 - Git style strings (foreground color, background color, font attributes) are supported for >20 stylable elements
 - Side-by-side view with line-wrapping
 - Line numbering
+- Handles grep output with file paths from `rg`, `git grep`, `grep`, etc
 - `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.
@@ -410,6 +413,15 @@ In contrast, the long replacement line in the right panel overflows by almost an
 For control over the details of line wrapping, see `--wrap-max-lines`, `--wrap-left-symbol`, `--wrap-right-symbol`, `--wrap-right-percent`, `--wrap-right-prefix-symbol`, `--inline-hint-style`.
 Line wrapping was implemented by @th1000s.
 
+### Grep
+
+Delta applies syntax-highlighting and other enhancements to standard grep output such as from `git grep`, [ripgrep](https://github.com/BurntSushi/ripgrep/) (aka `rg`), grep, etc.
+To use with `git grep`, set delta as the pager for `grep` in the `[pager]` section of your gitconfig. See the example at the [top of the page](#get-started).
+Output from other grep tools can be piped to delta: e.g. `rg -Hn --color=always`, `grep -Hn --color=always`, etc.
+To customize the colors and syntax highlighting, see `grep-match-line-style`, `grep-match-word-style`, `grep-contexct-line-style`, `grep-file-style`, `grep-line-number-style`.
+Ripgrep's `rg --json` output format is supported; this avoids certain file name parsing ambiguities that are inevitable with the standard grep output formats.
+Note that `git grep` can display the "function context" for matches and that delta handles this output specially: see the `-p` and `-W` options of `git grep`.
+
 ### "Features": named groups of settings
 
 All delta options can go under the `[delta]` section in your git config file. However, you can also use named "features" to keep things organized: these are sections in git config like `[delta "my-feature"]`. Here's an example using two custom features:

src/cli.rs

@@ -441,6 +441,40 @@ pub struct Opt {
     )]
     pub blame_timestamp_format: String,
 
+    #[structopt(long = "grep-match-line-style")]
+    /// Style (foreground, background, attributes) for matching lines of code in
+    /// grep output. See STYLES section. Defaults to plus-style.
+    pub grep_match_line_style: Option<String>,
+
+    #[structopt(long = "grep-match-word-style")]
+    /// Style (foreground, background, attributes) for the specific matching
+    /// substrings within a matching line of code in grep output. See STYLES
+    /// section. Defaults to plus-style.
+    pub grep_match_word_style: Option<String>,
+
+    #[structopt(long = "grep-context-line-style")]
+    /// Style (foreground, background, attributes) for non-matching lines of
+    /// code in grep output. See STYLES section. Defaults to zero-style.
+    pub grep_context_line_style: Option<String>,
+
+    #[structopt(long = "grep-file-style")]
+    /// Style (foreground, background, attributes) for file paths in grep
+    /// output. See STYLES section. Defaults to hunk-header-file-path-style.
+    pub grep_file_style: Option<String>,
+
+    #[structopt(long = "grep-line-number-style")]
+    /// Style (foreground, background, attributes) for line numbers in grep
+    /// output. See STYLES section. Defaults to hunk-header-line-number-style.
+    pub grep_line_number_style: Option<String>,
+
+    #[structopt(long = "grep-separator-symbol", default_value = ":")]
+    /// Symbol used in grep output to separate file path (and line number) from
+    /// the line of file contents. Defaults to ":" for both match and context
+    /// lines, since many terminal emulators recognize constructs like
+    /// "/path/to/file:7:". However, standard grep output uses "-" for context
+    /// lines: set this option to "keep" to keep the original separator symbols.
+    pub grep_separator_symbol: 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)

src/config.rs

@@ -80,6 +80,12 @@ pub struct Config {
     pub git_config: Option<GitConfig>,
     pub git_minus_style: Style,
     pub git_plus_style: Style,
+    pub grep_context_line_style: Style,
+    pub grep_file_style: Style,
+    pub grep_line_number_style: Style,
+    pub grep_match_line_style: Style,
+    pub grep_match_word_style: Style,
+    pub grep_separator_symbol: String,
     pub hunk_header_file_style: Style,
     pub hunk_header_line_number_style: Style,
     pub hunk_header_style_include_file_path: bool,
@@ -243,6 +249,12 @@ impl From<cli::Opt> for Config {
             file_style: styles["file-style"],
             git_config: opt.git_config,
             git_config_entries: opt.git_config_entries,
+            grep_context_line_style: styles["grep-context-line-style"],
+            grep_file_style: styles["grep-file-style"],
+            grep_line_number_style: styles["grep-line-number-style"],
+            grep_match_line_style: styles["grep-match-line-style"],
+            grep_match_word_style: styles["grep-match-word-style"],
+            grep_separator_symbol: opt.grep_separator_symbol,
             hunk_header_file_style: styles["hunk-header-file-style"],
             hunk_header_line_number_style: styles["hunk-header-line-number-style"],
             hunk_header_style: styles["hunk-header-style"],

src/delta.rs

@@ -23,6 +23,7 @@ pub enum State {
     SubmoduleLog, // In a submodule section, with gitconfig diff.submodule = log
     SubmoduleShort(String), // In a submodule section, with gitconfig diff.submodule = short
     Blame(String, Option<String>), // In a line of `git blame` output (commit, repeat_blame_line).
+    Grep,     // In a line of `git grep` output
     Unknown,
     // The following elements are created when a line is wrapped to display it:
     HunkZeroWrapped,  // Wrapped unchanged line
@@ -121,6 +122,7 @@ impl<'a> StateMachine<'a> {
                 || self.handle_submodule_short_line()?
                 || self.handle_hunk_line()?
                 || self.handle_blame_line()?
+                || self.handle_grep_line()?
                 || self.should_skip_line()
                 || self.emit_line_unchanged()?;
         }
@@ -133,7 +135,13 @@ impl<'a> StateMachine<'a> {
     fn ingest_line(&mut self, raw_line_bytes: &[u8]) {
         // TODO: retain raw_line as Cow
         self.raw_line = String::from_utf8_lossy(raw_line_bytes).to_string();
-        if self.config.max_line_length > 0 && self.raw_line.len() > self.config.max_line_length {
+        if self.config.max_line_length > 0
+            && self.raw_line.len() > self.config.max_line_length
+            // We must not truncate ripgrep --json output
+            // TODO: An alternative might be to truncate `line` but retain
+            // `raw_line` untruncated?
+            && !self.raw_line.starts_with('{')
+        {
             self.raw_line = ansi::truncate_str(
                 &self.raw_line,
                 self.config.max_line_length,

src/handlers/file_meta.rs

@@ -210,7 +210,7 @@ fn get_file_extension_from_file_meta_line_file_path(path: &str) -> Option<&str>
 }
 
 /// Attempt to parse input as a file path and return extension as a &str.
-fn get_extension(s: &str) -> Option<&str> {
+pub fn get_extension(s: &str) -> Option<&str> {
     let path = Path::new(s);
     path.extension()
         .and_then(|e| e.to_str())