Add `diff --short` that lists changes without showing them

Dependencies

• [2] SXEYMYF7 Fixing the bad changes in history (unfortunately, by rebooting).

Change contents

• edit in pijul/src/commands/diff.rs at line 22
  [2.174004]

  [2.174004]
  + #[clap(long = "short")]

  + pub short: bool,
• edit in pijul/src/commands/diff.rs at line 104
  [2.177020]

  [2.177020]
  + } else if self.short {

  + let mut changes = Vec::new();

  + for ch in change.changes.iter() {

  + changes.push(match ch {

  + Record::FileMove { path, .. } =>

  + format!("MV {}\n", path),

  + Record::FileDel { path, .. } =>

  + format!("D {}\n", path),

  + Record::FileUndel { path, .. } =>

  + format!("UD {}\n", path),

  + Record::FileAdd { path, .. } =>

  + format!("A {}", path),

  + Record::SolveNameConflict { path, .. } =>

  + format!("SC {}", path),

  + Record::UnsolveNameConflict { path, .. } =>

  + format!("UC {}", path),

  + Record::Edit { local: Local { path, .. }, .. } =>

  + format!("M {}", path),

  + Record::Replacement { local: Local { path, .. }, .. } =>

  + format!("R {}", path),

  + Record::SolveOrderConflict { local: Local { path, .. }, .. } =>

  + format!("SC {}", path),

  + Record::UnsolveOrderConflict { local: Local { path, .. }, .. } =>

  + format!("UC {}", path),

  + Record::ResurrectZombies { local: Local { path, .. }, .. } =>

  + format!("RZ {}", path),

  + });

  + }

  + changes.sort_unstable();

  + changes.dedup();

  + for ch in changes { println!("{}", ch); }
• edit in libpijul/src/working_copy/filesystem.rs at line 114
  [2.212689]→[2.212689:212753](∅→∅)
  − eprintln!("Adding {:?}", path);
• edit in libpijul/src/working_copy/filesystem.rs at line 126
  [2.213373]→[2.213373:213429](∅→∅)
  − eprintln!("Adding {:?}", path);