Add support for irreversible-delete

Fix #128

Add support for `git diff -D` (aka irreversible delete)

The patch is adding a title for removed file, even when there is no file content in the diff output
Without the patch, there was no output related to the file at all

4 files changed, 127 insertions, 34 deletions

diff --git a/src/delta.rs b/src/delta.rs
index 7ba29973..27b30512 100644
--- a/src/delta.rs
+++ b/src/delta.rs
@@ -157,6 +157,7 @@ impl<'a> StateMachine<'a> {
             let _ = self.handle_commit_meta_header_line()?
                 || self.handle_diff_stat_line()?
                 || self.handle_diff_header_diff_line()?
+                || self.handle_diff_header_file_operation_line()?
                 || self.handle_diff_header_minus_line()?
                 || self.handle_diff_header_plus_line()?
                 || self.handle_hunk_header_line()?
@@ -173,7 +174,7 @@ impl<'a> StateMachine<'a> {
                 || self.emit_line_unchanged()?;
         }
 
-        self.handle_pending_mode_line_with_diff_name()?;
+        self.handle_pending_line_with_diff_name()?;
         self.painter.paint_buffered_minus_and_plus_lines();
         self.painter.emit()?;
         Ok(())
diff --git a/src/handlers/diff_header.rs b/src/handlers/diff_header.rs
index 3e317bee..39262c1b 100644
--- a/src/handlers/diff_header.rs
+++ b/src/handlers/diff_header.rs
@@ -14,9 +14,11 @@ const DIFF_PREFIXES: [&str; 6] = ["a/", "b/", "c/", "i/", "o/", "w/"];
 
 #[derive(Debug, PartialEq)]
 pub enum FileEvent {
+    Added,
     Change,
     Copy,
     Rename,
+    Removed,
     NoEvent,
 }
 
@@ -49,6 +51,25 @@ impl<'a> StateMachine<'a> {
         Ok(handled_line)
     }
 
+    fn should_write_generic_diff_header_header_line(&mut self) -> std::io::Result<bool> {
+        // In color_only mode, raw_line's structure shouldn't be changed.
+        // So it needs to avoid fn _handle_diff_header_header_line
+        // (it connects the plus_file and minus_file),
+        // and to call fn handle_generic_diff_header_header_line directly.
+        if self.config.color_only {
+            write_generic_diff_header_header_line(
+                &self.line,
+                &self.raw_line,
+                &mut self.painter,
+                &mut self.mode_info,
+                self.config,
+            )?;
+            Ok(true)
+        } else {
+            Ok(false)
+        }
+    }
+
     #[inline]
     fn test_diff_header_minus_line(&self) -> bool {
         (matches!(self.state, State::DiffHeader(_)) || self.source == Source::DiffUnified)
@@ -62,7 +83,6 @@ impl<'a> StateMachine<'a> {
         if !self.test_diff_header_minus_line() {
             return Ok(false);
         }
-        let mut handled_line = false;
 
         let (path_or_mode, file_event) =
             parse_diff_header_line(&self.line, self.source == Source::GitDiff);
@@ -84,21 +104,7 @@ impl<'a> StateMachine<'a> {
         }
 
         self.painter.paint_buffered_minus_and_plus_lines();
-        // In color_only mode, raw_line's structure shouldn't be changed.
-        // So it needs to avoid fn _handle_diff_header_header_line
-        // (it connects the plus_file and minus_file),
-        // and to call fn handle_generic_diff_header_header_line directly.
-        if self.config.color_only {
-            write_generic_diff_header_header_line(
-                &self.line,
-                &self.raw_line,
-                &mut self.painter,
-                &mut self.mode_info,
-                self.config,
-            )?;
-            handled_line = true;
-        }
-        Ok(handled_line)
+        self.should_write_generic_diff_header_header_line()
     }
 
     #[inline]
@@ -129,25 +135,58 @@ impl<'a> StateMachine<'a> {
         self.current_file_pair = Some((self.minus_file.clone(), self.plus_file.clone()));
 
         self.painter.paint_buffered_minus_and_plus_lines();
-        // In color_only mode, raw_line's structure shouldn't be changed.
-        // So it needs to avoid fn _handle_diff_header_header_line
-        // (it connects the plus_file and minus_file),
-        // and to call fn handle_generic_diff_header_header_line directly.
-        if self.config.color_only {
-            write_generic_diff_header_header_line(
-                &self.line,
-                &self.raw_line,
-                &mut self.painter,
-                &mut self.mode_info,
-                self.config,
-            )?;
-            handled_line = true
+        if self.should_write_generic_diff_header_header_line()? {
+            handled_line = true;
         } else if self.should_handle()
             && self.handled_diff_header_header_line_file_pair != self.current_file_pair
         {
             self.painter.emit()?;
             self._handle_diff_header_header_line(self.source == Source::DiffUnified)?;
-            self.handled_diff_header_header_line_file_pair = self.current_file_pair.clone()
+            self.handled_diff_header_header_line_file_pair = self.current_file_pair.clone();
+        }
+        Ok(handled_line)
+    }
+
+    #[inline]
+    fn test_diff_header_file_operation_line(&self) -> bool {
+        (matches!(self.state, State::DiffHeader(_)) || self.source == Source::DiffUnified)
+            && (self.line.starts_with("deleted file mode ")
+                || self.line.starts_with("new file mode "))
+    }
+
+    /// Check for and handle the "deleted file ..."  line.
+    pub fn handle_diff_header_file_operation_line(&mut self) -> std::io::Result<bool> {
+        if !self.test_diff_header_file_operation_line() {
+            return Ok(false);
+        }
+        let mut handled_line = false;
+        let (_mode_info, file_event) =
+            parse_diff_header_line(&self.line, self.source == Source::GitDiff);
+        let name = get_repeated_file_path_from_diff_line(&self.diff_line)
+            .unwrap_or_else(|| "".to_string());
+        match file_event {
+            FileEvent::Removed => {
+                self.minus_file = name;
+                self.plus_file = "/dev/null".into();
+                self.minus_file_event = FileEvent::Change;
+                self.plus_file_event = FileEvent::Change;
+                self.current_file_pair = Some((self.minus_file.clone(), self.plus_file.clone()));
+            }
+            FileEvent::Added => {
+                self.minus_file = "/dev/null".into();
+                self.plus_file = name;
+                self.minus_file_event = FileEvent::Change;
+                self.plus_file_event = FileEvent::Change;
+                self.current_file_pair = Some((self.minus_file.clone(), self.plus_file.clone()));
+            }
+            _ => (),
+        }
+
+        if self.should_write_generic_diff_header_header_line()?
+            || (self.should_handle()
+                && self.handled_diff_header_header_line_file_pair != self.current_file_pair)
+        {
+            handled_line = true;
         }
         Ok(handled_line)
     }
@@ -172,7 +211,16 @@ impl<'a> StateMachine<'a> {
         )
     }
 
-    pub fn handle_pending_mode_line_with_diff_name(&mut self) -> std::io::Result<()> {
+    #[inline]
+    fn test_pending_line_with_diff_name(&self) -> bool {
+        matches!(self.state, State::DiffHeader(_)) || self.source == Source::DiffUnified
+    }
+
+    pub fn handle_pending_line_with_diff_name(&mut self) -> std::io::Result<()> {
+        if !self.test_pending_line_with_diff_name() {
+            return Ok(());
+        }
+
         if !self.mode_info.is_empty() {
             let format_label = |label: &str| {
                 if !label.is_empty() {
@@ -204,6 +252,13 @@ impl<'a> StateMachine<'a> {
                 &mut self.mode_info,
                 self.config,
             )
+        } else if !self.config.color_only
+            && self.should_handle()
+            && self.handled_diff_header_header_line_file_pair != self.current_file_pair
+        {
+            self._handle_diff_header_header_line(self.source == Source::DiffUnified)?;
+            self.handled_diff_header_header_line_file_pair = self.current_file_pair.clone();
+            Ok(())
         } else {
             Ok(())
         }
@@ -292,6 +347,12 @@ fn parse_diff_header_line(line: &str, git_diff_name: bool) -> (String, FileEvent
         line if line.starts_with("copy to ") => {
             (line[8..].to_string(), FileEvent::Copy) // "copy to ".len()
         }
+        line if line.starts_with("new file mode ") => {
+            (line[14..].to_string(), FileEvent::Added) // "new file mode ".len()
+        }
+        line if line.starts_with("deleted file mode ") => {
+            (line[18..].to_string(), FileEvent::Removed) // "deleted file mode ".len()
+        }
         _ => ("".to_string(), FileEvent::NoEvent),
     }
 }
diff --git a/src/handlers/diff_header_diff.rs b/src/handlers/diff_header_diff.rs
index fdd2d39a..a79f6e1c 100644
--- a/src/handlers/diff_header_diff.rs
+++ b/src/handlers/diff_header_diff.rs
@@ -22,7 +22,7 @@ impl<'a> StateMachine<'a> {
             } else {
                 State::DiffHeader(DiffType::Unified)
             };
-        self.handle_pending_mode_line_with_diff_name()?;
+        self.handle_pending_line_with_diff_name()?;
         self.handled_diff_header_header_line_file_pair = None;
         self.diff_line = self.line.clone();
         if !self.should_skip_line() {
diff --git a/src/tests/test_example_diffs.rs b/src/tests/test_example_diffs.rs
index 2eca792f..325f2e9a 100644
--- a/src/tests/test_example_diffs.rs
+++ b/src/tests/test_example_diffs.rs
@@ -17,7 +17,6 @@ mod tests {
     }
 
     #[test]
-    #[ignore] // #128
     fn test_added_empty_file() {
         DeltaTest::with_args(&[])
             .with_input(ADDED_EMPTY_FILE)
@@ -1571,6 +1570,21 @@ src/align.rs:71: impl<'a> Alignment<'a> { │
     }
 
     #[test]
+    fn test_file_deleted_without_preimage() {
+        DeltaTest::with_args(&[])
+            .with_input(GIT_DIFF_FILE_DELETED_WITHOUT_PREIMAGE)
+            .expect_contains("removed: foo.bar");
+    }
+
+    #[test]
+    fn test_files_deleted_without_preimage() {
+        DeltaTest::with_args(&[])
+            .with_input(GIT_DIFF_FILES_DELETED_WITHOUT_PREIMAGE)
+            .expect_contains("removed: foo")
+            .expect_contains("removed: bar");
+    }
+
+    #[test]
     fn test_file_mode_change_with_diff() {
         DeltaTest::with_args(&["--navigate", "--keep-plus-minus-markers"])
             .with_input(GIT_DIFF_FILE_MODE_CHANGE_WITH_DIFF)
@@ -2334,6 +2348,23 @@ old mode 100700
 new mode 100644
 ";
 
+    // This output can be generated with `git diff -D`
+    const GIT_DIFF_FILE_DELETED_WITHOUT_PREIMAGE: &str = "
+diff --git a/foo.bar b/foo.bar
+deleted file mode 100644
+index e019be0..0000000
+";
+
+    // This output can be generated with `git diff -D`
+    const GIT_DIFF_FILES_DELETED_WITHOUT_PREIMAGE: &str = "
+diff --git a/foo b/foo
+deleted file mode 100644
+index e019be0..0000000
+diff --git a/bar b/bar
+deleted file mode 100644
+index e019be0..0000000
+";
+
     const GIT_DIFF_FILE_MODE_CHANGE_WITH_DIFF: &str = "
 diff --git a/src/script b/src/script
 old mode 100644