Output paths relative to current working directory

Fixes #552

5 files changed, 126 insertions, 19 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 96844e15..0db780e7 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -272,6 +272,7 @@ dependencies = [
  "git2",
  "itertools",
  "lazy_static",
+ "pathdiff",
  "regex",
  "shell-words",
  "structopt",
@@ -497,6 +498,12 @@ dependencies = [
 ]
 
 [[package]]
+name = "pathdiff"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "877630b3de15c0b64cc52f659345724fbf6bdad9bd9566699fc53688f3c34a34"
+
+[[package]]
 name = "percent-encoding"
 version = "2.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
diff --git a/Cargo.toml b/Cargo.toml
index b4e003e0..55ec3b0b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -25,6 +25,7 @@ console = "0.14.1"
 dirs-next = "2.0.0"
 itertools = "0.10.0"
 lazy_static = "1.4"
+pathdiff = "0.2.0"
 regex = "1.4.6"
 shell-words = "1.0.0"
 structopt = "0.3.21"
diff --git a/src/config.rs b/src/config.rs
index f822efc2..c6719839 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -23,6 +23,7 @@ pub struct Config {
     pub background_color_extends_to_terminal_width: bool,
     pub commit_style: Style,
     pub color_only: bool,
+    pub cwd_relative_to_repo_root: Option<String>,
     pub decorations_width: cli::Width,
     pub error_exit_code: i32,
     pub file_added_label: String,
@@ -182,6 +183,7 @@ impl From<cli::Opt> for Config {
                 .background_color_extends_to_terminal_width,
             commit_style,
             color_only: opt.color_only,
+            cwd_relative_to_repo_root: std::env::var("GIT_PREFIX").ok(),
             decorations_width: opt.computed.decorations_width,
             error_exit_code: 2, // Use 2 for error because diff uses 0 and 1 for non-error.
             file_added_label,
diff --git a/src/delta.rs b/src/delta.rs
index 7d52eae1..869bd4a4 100644
--- a/src/delta.rs
+++ b/src/delta.rs
@@ -113,6 +113,8 @@ impl<'a> StateMachine<'a> {
 
             let mut handled_line = if line.starts_with("commit ") {
                 self.handle_commit_meta_header_line()?
+            } else if self.state == State::CommitMeta && line.starts_with(" ") {
+                self.handle_diff_stat_line()?
             } else if line.starts_with("diff ") {
                 self.handle_file_meta_diff_line()?
             } else if (self.state == State::FileMeta || self.source == Source::DiffUnified)
@@ -226,6 +228,20 @@ impl<'a> StateMachine<'a> {
         Ok(())
     }
 
+    fn handle_diff_stat_line(&mut self) -> std::io::Result<bool> {
+        let mut handled_line = false;
+        if let Some(cwd) = self.config.cwd_relative_to_repo_root.as_deref() {
+            if let Some(replacement_line) =
+                parse::relativize_path_in_diff_stat_line(&self.raw_line, cwd)
+            {
+                self.painter.emit()?;
+                writeln!(self.painter.writer, "{}", replacement_line)?;
+                handled_line = true
+            }
+        }
+        Ok(handled_line)
+    }
+
     #[allow(clippy::unnecessary_wraps)]
     fn handle_file_meta_diff_line(&mut self) -> std::io::Result<bool> {
         self.painter.paint_buffered_minus_and_plus_lines();
@@ -237,8 +253,11 @@ impl<'a> StateMachine<'a> {
     fn handle_file_meta_minus_line(&mut self) -> std::io::Result<bool> {
         let mut handled_line = false;
 
-        let parsed_file_meta_line =
-            parse::parse_file_meta_line(&self.line, self.source == Source::GitDiff);
+        let parsed_file_meta_line = parse::parse_file_meta_line(
+            &self.line,
+            self.source == Source::GitDiff,
+            self.config.cwd_relative_to_repo_root.as_deref(),
+        );
         self.minus_file = parsed_file_meta_line.0;
         self.file_event = parsed_file_meta_line.1;
 
@@ -271,8 +290,11 @@ impl<'a> StateMachine<'a> {
 
     fn handle_file_meta_plus_line(&mut self) -> std::io::Result<bool> {
         let mut handled_line = false;
-        let parsed_file_meta_line =
-            parse::parse_file_meta_line(&self.line, self.source == Source::GitDiff);
+        let parsed_file_meta_line = parse::parse_file_meta_line(
+            &self.line,
+            self.source == Source::GitDiff,
+            self.config.cwd_relative_to_repo_root.as_deref(),
+        );
         self.plus_file = parsed_file_meta_line.0;
         self.painter
             .set_syntax(parse::get_file_extension_from_file_meta_line_file_path(
diff --git a/src/parse.rs b/src/parse.rs
index 4c2cf233..65ad72f1 100644
--- a/src/parse.rs
+++ b/src/parse.rs
@@ -28,8 +28,12 @@ pub enum FileEvent {
     NoEvent,
 }
 
-pub fn parse_file_meta_line(line: &str, git_diff_name: bool) -> (String, FileEvent) {
-    match line {
+pub fn parse_file_meta_line(
+    line: &str,
+    git_diff_name: bool,
+    cwd_relative_to_repo_root: Option<&str>,
+) -> (String, FileEvent) {
+    let (mut path, file_event) = match line {
         line if line.starts_with("--- ") || line.starts_with("+++ ") => {
             let offset = 4;
             let file = match &line[offset..] {
@@ -56,7 +60,44 @@ pub fn parse_file_meta_line(line: &str, git_diff_name: bool) -> (String, FileEve
             (line[8..].to_string(), FileEvent::Copy) // "copy to ".len()
         }
         _ => ("".to_string(), FileEvent::NoEvent),
+    };
+
+    if let Some(cwd) = cwd_relative_to_repo_root {
+        if let Some(relative_path) = pathdiff::diff_paths(&path, cwd) {
+            if let Some(relative_path) = relative_path.to_str() {
+                path = relative_path.to_owned();
+            }
+        }
+    }
+
+    (path, file_event)
+}
+
+// A regex to capture the path, and the content from the pipe onwards, in lines
+// like these:
+// " src/delta.rs  | 14 ++++++++++----"
+// " src/config.rs |  2 ++"
+lazy_static! {
+    static ref DIFF_STAT_LINE_REGEX: Regex =
+        Regex::new(r" ([^\| ][^\|]+[^\| ]) +(\| +[0-9]+ .+)").unwrap();
+}
+
+pub fn relativize_path_in_diff_stat_line(
+    line: &str,
+    cwd_relative_to_repo_root: &str,
+) -> Option<String> {
+    if let Some(caps) = DIFF_STAT_LINE_REGEX.captures(line) {
+        let path_relative_to_repo_root = caps.get(1).unwrap().as_str();
+        if let Some(relative_path) =
+            pathdiff::diff_paths(path_relative_to_repo_root, cwd_relative_to_repo_root)
+        {
+            if let Some(relative_path) = relative_path.to_str() {
+                let suffix = caps.get(2).unwrap().as_str();
+                return Some(format!(" {:<30}{}", relative_path, suffix,));
+            }
+        }
     }
+    return None;
 }
 
 pub fn get_file_extension_from_file_meta_line_file_path(path: &str) -> Option<&str> {
@@ -245,21 +286,21 @@ mod tests {
     #[test]
     fn test_get_file_path_from_git_file_meta_line() {
         assert_eq!(
-            parse_file_meta_line("--- /dev/null", true),
+            parse_file_meta_line("--- /dev/null", true, None),
             ("/dev/null".to_string(), FileEvent::Change)
         );
         for prefix in &DIFF_PREFIXES {
             assert_eq!(
-                parse_file_meta_line(&format!("--- {}src/delta.rs", prefix), true),
+                parse_file_meta_line(&format!("--- {}src/delta.rs", prefix), true, None),
                 ("src/delta.rs".to_string(), FileEvent::Change)
             );
         }
         assert_eq!(
-            parse_file_meta_line("--- src/delta.rs", true),
+            parse_file_meta_line("--- src/delta.rs", true, None),
             ("src/delta.rs".to_string(), FileEvent::Change)
         );
         assert_eq!(
-            parse_file_meta_line("+++ src/delta.rs", true),
+            parse_file_meta_line("+++ src/delta.rs", true, None),
             ("src/delta.rs".to_string(), FileEvent::Change)
         );
     }
@@ -267,23 +308,23 @@ mod tests {
     #[test]
     fn test_get_file_path_from_git_file_meta_line_containing_spaces() {
         assert_eq!(
-            parse_file_meta_line("+++ a/my src/delta.rs", true),
+            parse_file_meta_line("+++ a/my src/delta.rs", true, None),
             ("my src/delta.rs".to_string(), FileEvent::Change)
         );
         assert_eq!(
-            parse_file_meta_line("+++ my src/delta.rs", true),
+            parse_file_meta_line("+++ my src/delta.rs", true, None),
             ("my src/delta.rs".to_string(), FileEvent::Change)
         );
         assert_eq!(
-            parse_file_meta_line("+++ a/src/my delta.rs", true),
+            parse_file_meta_line("+++ a/src/my delta.rs", true, None),
             ("src/my delta.rs".to_string(), FileEvent::Change)
         );
         assert_eq!(
-            parse_file_meta_line("+++ a/my src/my delta.rs", true),
+            parse_file_meta_line("+++ a/my src/my delta.rs", true, None),
             ("my src/my delta.rs".to_string(), FileEvent::Change)
         );
         assert_eq!(
-            parse_file_meta_line("+++ b/my src/my enough/my delta.rs", true),
+            parse_file_meta_line("+++ b/my src/my enough/my delta.rs", true, None),
             (
                 "my src/my enough/my delta.rs".to_string(),
                 FileEvent::Change
@@ -294,7 +335,7 @@ mod tests {
     #[test]
     fn test_get_file_path_from_git_file_meta_line_rename() {
         assert_eq!(
-            parse_file_meta_line("rename from nospace/file2.el", true),
+            parse_file_meta_line("rename from nospace/file2.el", true, None),
             ("nospace/file2.el".to_string(), FileEvent::Rename)
         );
     }
@@ -302,7 +343,7 @@ mod tests {
     #[test]
     fn test_get_file_path_from_git_file_meta_line_rename_containing_spaces() {
         assert_eq!(
-            parse_file_meta_line("rename from with space/file1.el", true),
+            parse_file_meta_line("rename from with space/file1.el", true, None),
             ("with space/file1.el".to_string(), FileEvent::Rename)
         );
     }
@@ -310,11 +351,11 @@ mod tests {
     #[test]
     fn test_parse_file_meta_line() {
         assert_eq!(
-            parse_file_meta_line("--- src/delta.rs", false),
+            parse_file_meta_line("--- src/delta.rs", false, None),
             ("src/delta.rs".to_string(), FileEvent::Change)
         );
         assert_eq!(
-            parse_file_meta_line("+++ src/delta.rs", false),
+            parse_file_meta_line("+++ src/delta.rs", false, None),
             ("src/delta.rs".to_string(), FileEvent::Change)
         );
     }
@@ -369,4 +410,38 @@ mod tests {
         assert_eq!(line_numbers_and_hunk_lengths[1], (358, 15),);
         assert_eq!(line_numbers_and_hunk_lengths[2], (358, 16),);
     }
+
+    #[test]
+    fn test_relative_path() {
+        for (path, cwd_relative_to_repo_root, expected) in &[
+            ("file.rs", "", "file.rs"),
+            ("file.rs", "a/", "../file.rs"),
+            ("a/file.rs", "a/", "file.rs"),
+            ("a/b/file.rs", "a", "b/file.rs"),
+            ("c/d/file.rs", "a/b/", "../../c/d/file.rs"),
+        ] {
+            assert_eq!(
+                pathdiff::diff_paths(path, cwd_relative_to_repo_root),
+                Some(expected.into())
+            )
+        }
+    }
+
+    #[test]
+    fn test_diff_stat_line_regex_1() {
+        let caps = DIFF_STAT_LINE_REGEX.captures(" src/delta.rs  | 14 ++++++++++----");
+        assert!(caps.is_some());
+        let caps = caps.unwrap();
+        assert_eq!(caps.get(1).unwrap().as_str(), "src/delta.rs");
+        assert_eq!(caps.get(2).unwrap().as_str(), "| 14 ++++++++++----");
+    }
+
+    #[test]
+    fn test_diff_stat_line_regex_2() {
+        let caps = DIFF_STAT_LINE_REGEX.captures(" src/config.rs |  2 ++");
+        assert!(caps.is_some());
+        let caps = caps.unwrap();
+        assert_eq!(caps.get(1).unwrap().as_str(), "src/config.rs");
+        assert_eq!(caps.get(2).unwrap().as_str(), "|  2 ++");
+    }
 }