print coloured text correctly given line terminator is not included

Dependencies

• [2] ZRUPLBBT Colours in diff and change: separating concerns and dependencies
• [3] SXEYMYF7 Fixing the bad changes in history (unfortunately, by rebooting).
• [4] 5BB266P6 Optional colours in the global config file

Change contents

• replacement in pijul/src/commands/diff.rs at line 212
  [2.1196]→[2.1196:1250](∅→∅)
  − write!(self.w, "{} {}", pref, contents)?;
  [2.1196]

  [2.1250]
  + writeln!(self.w, "{} {}", pref, contents)?;
• replacement in pijul/src/commands/diff.rs at line 215
  [2.1294]→[2.1294:1346](∅→∅)
  − write!(self.w, "{} {}", pref, contents)
  [2.1294]

  [2.1346]
  + writeln!(self.w, "{} {}", pref, contents)