repo_description: A cat(1) clone with wings.
repo_topics: cli command-line git hacktoberfest rust syntax-highlighting terminal tool
code: #![cfg(feature = "git")]
  
  use std::collections::HashMap;
  use std::fs;
  use std::path::Path;
  
  use git2::{DiffOptions, IntoCString, Repository};
  
  #[derive(Copy, Clone, Debug)]
  pub enum LineChange {
      Added,
      RemovedAbove,
      RemovedBelow,
      Modified,
  }
  
  pub type LineChanges = HashMap<u32, LineChange>;
  
  pub fn get_git_diff(filename: &Path) -> Option<LineChanges> {
      let repo = Repository::discover(filename).ok()?;
  
      let repo_path_absolute = fs::canonicalize(repo.workdir()?).ok()?;
  
      let filepath_absolute = fs::canonicalize(filename).ok()?;
      let filepath_relative_to_repo = filepath_absolute.strip_prefix(&repo_path_absolute).ok()?;
  
      let mut diff_options = DiffOptions::new();
      let pathspec = filepath_relative_to_repo.into_c_string().ok()?;
      diff_options.pathspec(pathspec);
      diff_options.context_lines(0);
  
      let diff = repo
          .diff_index_to_workdir(None, Some(&mut diff_options))
          .ok()?;
  
      let mut line_changes: LineChanges = HashMap::new();
  
      let mark_section =
          |line_changes: &mut LineChanges, start: u32, end: i32, change: LineChange| {
              for line in start..=end as u32 {
                  line_changes.insert(line, change);
              }
          };
  
      let _ = diff.foreach(
          &mut |_, _| true,
          None,
          Some(&mut |delta, hunk| {
              let path = delta.new_file().path().unwrap_or_else(|| Path::new(""));
  
              if filepath_relative_to_repo != path {
                  return false;
              }
  
              let old_lines = hunk.old_lines();
              let new_start = hunk.new_start();
              let new_lines = hunk.new_lines();
              let new_end = (new_start + new_lines) as i32 - 1;
  
              if old_lines == 0 && new_lines > 0 {
                  mark_section(&mut line_changes, new_start, new_end, LineChange::Added);
              } else if new_lines == 0 && old_lines > 0 {
                  if new_start == 0 {
                      mark_section(&mut line_changes, 1, 1, LineChange::RemovedAbove);
                  } else {
                      mark_section(
                          &mut line_changes,
                          new_start,
                          new_start as i32,
                          LineChange::RemovedBelow,
                      );
                  }
              } else {
                  mark_section(&mut line_changes, new_start, new_end, LineChange::Modified);
              }
  
              true
          }),
          None,
      );
  
      Some(line_changes)
  }
  