Fixing a bug when outputting changes in text format

Dependencies

• [2] ZSF3YFZT encoded file deletion
• [3] VO5OQW4W Removing anyhow in libpijul
• [4] X243Z3Y5 Recording only the required metadata (can even be changed later!)
• [5] 3S6LU2U5 abstract out FileMetadata (de)serialistion

Change contents

• replacement in libpijul/src/change/text_changes.rs at line 333
  [2.4797]→[3.2798:2860](∅→∅),[3.2798]→[3.2798:2860](∅→∅)
  − } = FileMetadata::read(&change_contents);
  [2.4797]

  [3.1482]
  + } = FileMetadata::read(&change_contents[add.start.0.into()..add.end.0.into()]);
• replacement in libpijul/src/change/text_changes.rs at line 431
  [2.5444]→[3.2981:3043](∅→∅),[3.2981]→[3.2981:3043](∅→∅)
  − } = FileMetadata::read(&change_contents);
  [2.5444]

  [3.52241]
  + } = FileMetadata::read(&change_contents[n.start.0.into()..n.end.0.into()]);