Short options for pijul diff. This makes it possible to get unrecorded files using `pijul diff -su`.

Dependencies

• [2] HSEYMLO2 Adding an untracked change iterator
• [3] KWAMD2KR A few fixes in the documentation comments
• [4] SXEYMYF7 Fixing the bad changes in history (unfortunately, by rebooting).
• [5] YDKNUL6B Add `diff --short` that lists changes without showing them

Change contents

• replacement in "pijul/src/commands/diff.rs" at line 28
  [3.3164]→[3.0:28](∅→∅),[3.174004]→[3.0:28](∅→∅)
  − #[clap(long = "short")]
  [3.3164]

  [3.28]
  + #[clap(short = 's', long = "short")]
• replacement in "pijul/src/commands/diff.rs" at line 31
  [2.145]→[2.145:177](∅→∅)
  − #[clap(long = "untracked")]
  [2.145]

  [2.177]
  + #[clap(short = 'u', long = "untracked")]