Fixing an error message in unrecord

Dependencies

• [2] 3AMEP2Y5 More convenient interface for channels
• [3] VO5OQW4W Removing anyhow in libpijul
• [4] SXEYMYF7 Fixing the bad changes in history (unfortunately, by rebooting).
• [5] CCLLB7OI Upgrading to Sanakirja 0.15 + version bump
• [6] GHO6DWPI Refactoring iterators

Change contents

• replacement in libpijul/src/unrecord/mod.rs at line 26
  [3.8211]→[3.8211:8326](∅→∅)
  − #[error("Change not in channel: {}", change_id.to_base32())]

  − ChangeIsDependedUpon { change_id: ChangeId },
  [3.8211]

  [3.8326]
  + #[error("Change {} is depended upon by {}", change_id.to_base32(), dependent.to_base32())]

  + ChangeIsDependedUpon { change_id: ChangeId, dependent: ChangeId },
• replacement in libpijul/src/unrecord/mod.rs at line 102
  [2.1014]→[3.9344:9419](∅→∅),[3.1661]→[3.9344:9419](∅→∅),[3.23438]→[3.9344:9419](∅→∅),[3.233360]→[3.9344:9419](∅→∅)
  − return Err(UnrecordError::ChangeIsDependedUpon { change_id });
  [2.1014]

  [3.233436]
  + return Err(UnrecordError::ChangeIsDependedUpon { change_id, dependent: d });