Syntax-highlight `git show $revision:./path/to/file.ext` output

5 files changed, 88 insertions, 7 deletions

diff --git a/src/delta.rs b/src/delta.rs
index bfb7761f..fa983a69 100644
--- a/src/delta.rs
+++ b/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).
+    GitShowFile, // In a line of `git show $revision:./path/to/file.ext` output
     Grep,     // In a line of `git grep` output
     Unknown,
     // The following elements are created when a line is wrapped to display it:
@@ -121,6 +122,7 @@ impl<'a> StateMachine<'a> {
                 || self.handle_submodule_log_line()?
                 || self.handle_submodule_short_line()?
                 || self.handle_hunk_line()?
+                || self.handle_git_show_file_line()?
                 || self.handle_blame_line()?
                 || self.handle_grep_line()?
                 || self.should_skip_line()
diff --git a/src/handlers/git_show_file.rs b/src/handlers/git_show_file.rs
new file mode 100644
index 00000000..2a4998ca
--- /dev/null
+++ b/src/handlers/git_show_file.rs
@@ -0,0 +1,33 @@
+use crate::delta::{State, StateMachine};
+use crate::paint::{BgShouldFill, StyleSectionSpecifier};
+use crate::utils::process;
+
+impl<'a> StateMachine<'a> {
+    // If this is a line of `git show $revision:/path/to/file.ext` output then
+    // syntax-highlight it as language `ext`.
+    pub fn handle_git_show_file_line(&mut self) -> std::io::Result<bool> {
+        self.painter.emit()?;
+        let mut handled_line = false;
+        if matches!(self.state, State::Unknown) {
+            if let Some(process::CallingProcess::GitShow(extension)) =
+                process::calling_process().as_deref()
+            {
+                self.state = State::GitShowFile;
+                self.painter.set_syntax(Some(extension));
+                self.painter.set_highlighter();
+            } else {
+                return Ok(handled_line);
+            }
+        }
+        if matches!(self.state, State::GitShowFile) {
+            self.painter.syntax_highlight_and_paint_line(
+                &self.line,
+                StyleSectionSpecifier::Style(self.config.zero_style),
+                self.state.clone(),
+                BgShouldFill::default(),
+            );
+            handled_line = true;
+        }
+        Ok(handled_line)
+    }
+}
diff --git a/src/handlers/mod.rs b/src/handlers/mod.rs
index e9f9b268..c032a7b9 100644
--- a/src/handlers/mod.rs
+++ b/src/handlers/mod.rs
@@ -7,6 +7,7 @@ pub mod draw;
 pub mod file_meta;
 pub mod file_meta_diff;
 pub mod file_meta_misc;
+pub mod git_show_file;
 pub mod grep;
 pub mod hunk;
 pub mod hunk_header;
diff --git a/src/paint.rs b/src/paint.rs
index 706dc5ce..529065f6 100644
--- a/src/paint.rs
+++ b/src/paint.rs
@@ -636,6 +636,7 @@ impl<'p> Painter<'p> {
             State::HunkHeader(_, _) => true,
             State::HunkMinus(Some(_)) | State::HunkPlus(Some(_)) => false,
             State::Blame(_, _) => true,
+            State::GitShowFile => true,
             State::Grep => true,
             State::Unknown
             | State::CommitMeta
diff --git a/src/utils/process.rs b/src/utils/process.rs
index 0000e9da..ee145f88 100644
--- a/src/utils/process.rs
+++ b/src/utils/process.rs
@@ -7,8 +7,9 @@ use lazy_static::lazy_static;
 
 #[derive(Clone, Debug, PartialEq)]
 pub enum CallingProcess {
-    GitGrep((HashSet<String>, HashSet<String>)),
-    OtherGrep, // rg, grep, ag, ack, etc
+    GitShow(String),                             // (extension)
+    GitGrep((HashSet<String>, HashSet<String>)), // ((long_options, short_options))
+    OtherGrep,                                   // rg, grep, ag, ack, etc
 }
 
 pub fn calling_process() -> Option<Cow<'static, CallingProcess>> {
@@ -79,14 +80,23 @@ pub fn describe_calling_process(args: &[String]) -> ProcessArgs<CallingProcess>
     match args.next() {
         Some(command) => match Path::new(command).file_stem() {
             Some(s) if s.to_str() == Some("git") => {
-                let mut args = args.skip_while(|s| *s != "grep");
+                let mut args = args.skip_while(|s| *s != "grep" && *s != "show");
                 match args.next() {
-                    Some(_) => {
+                    Some("grep") => {
                         ProcessArgs::Args(CallingProcess::GitGrep(parse_command_option_keys(args)))
                     }
-                    None => {
-                        // It's git, but not git grep. Don't look at any
-                        // more processes and return not-a-grep-command.
+                    Some("show") => {
+                        if let Some(extension) = get_git_show_file_extension(args) {
+                            ProcessArgs::Args(CallingProcess::GitShow(extension.to_string()))
+                        } else {
+                            // It's git show, but we failed to determine the
+                            // file extension. Don't look at any more processes.
+                            ProcessArgs::ArgError
+                        }
+                    }
+                    _ => {
+                        // It's git, but not a subcommand that we parse. Don't
+                        // look at any more processes.
                         ProcessArgs::ArgError
                     }
                 }
@@ -113,6 +123,18 @@ pub fn describe_calling_process(args: &[String]) -> ProcessArgs<CallingProcess>
     }
 }
 
+fn get_git_show_file_extension<'a>(args: impl Iterator<Item = &'a str>) -> Option<&'a str> {
+    if let Some(last_arg) = skip_uninteresting_args(args, "".split(' ')).last() {
+        // E.g. "HEAD~1:Makefile" or "775c3b8:./src/delta.rs"
+        match last_arg.split_once(':') {
+            Some((_, suffix)) => suffix.split('.').last(),
+            None => None,
+        }
+    } else {
+        None
+    }
+}
+
 // Skip all arguments starting with '-' from `args_it`. Also skip all arguments listed in
 // `skip_this_plus_parameter` plus their respective next argument.
 // Keep all arguments once a '--' is encountered.
@@ -716,6 +738,28 @@ pub mod tests {
     }
 
     #[test]
+    fn test_describe_calling_process_git_show() {
+        for (command, expected_extension) in [
+            ("/usr/local/bin/git show 775c3b84:./src/hello.rs", "rs"),
+            ("/usr/local/bin/git show HEAD~1:Makefile", "Makefile"),
+            (
+                "git -c x.y=z show --abbrev-commit 775c3b84:./src/hello.bye.R",
+                "R",
+            ),
+        ] {
+            let parent = MockProcInfo::with(&[
+                (2, 100, "-shell", None),
+                (3, 100, command, Some(2)),
+                (4, 100, "delta", Some(3)),
+            ]);
+            assert_eq!(
+                calling_process_cmdline(parent, describe_calling_process),
+                Some(CallingProcess::GitShow(expected_extension.to_string())),
+            );
+        }
+    }
+
+    #[test]
     fn test_process_calling_cmdline() {
         // Github runs CI tests for arm under qemu where where sysinfo can not find the parent process.
         if std::env::vars().any(|(key, _)| key == "CROSS_RUNNER" || key == "QEMU_LD_PREFIX") {