Current state: return zero instead of an Option if there is no change on the channel

Dependencies

• [2] VO5OQW4W Removing anyhow in libpijul
• [3] CVAT6LN3 Fixing git import, and adding more useful feedback (with `RUST_LOG="pijul=info"`)
• [4] SXEYMYF7 Fixing the bad changes in history (unfortunately, by rebooting).
• [5] WZVCLZKY address clippy lints
• [6] R3H7D42U Debugging `pijul git`: proper error reporting
• [7] BXD3IQYN Fixing --features git
• [8] I52XSRUH Massive cleanup, and simplification

Change contents

• replacement in pijul/src/commands/protocol.rs at line 201
  [3.131779]→[3.131779:131876](∅→∅)
  − if txn.current_state(&channel.borrow()) == Some(state) && extra.is_empty() {
  [3.131779]

  [3.131876]
  + if txn.current_state(&channel.borrow()) == state && extra.is_empty() {
• replacement in pijul/src/commands/git.rs at line 651
  [2.404]→[2.404:474](∅→∅)
  − return Ok(txn.current_state(&channel.borrow()).unwrap());
  [2.404]

  [2.474]
  + return Ok(txn.current_state(&channel.borrow()));
• replacement in pijul/src/commands/git.rs at line 676
  [3.160242]→[3.160242:160306](∅→∅),[3.160306]→[3.333:434](∅→∅),[3.434]→[3.160364:160370](∅→∅),[3.160364]→[3.160364:160370](∅→∅)
  − if let Some(state) = state {

  − Ok(state)

  − } else {

  − Ok(txn

  − .current_state(&channel.borrow())

  − .unwrap_or(Merkle::zero()))

  − }
  [3.160242]

  [3.160370]
  + Ok(state)
• replacement in pijul/src/commands/git.rs at line 736
  [3.161804]→[3.161804:161837](∅→∅)
  − Ok((n, Some(hash), Some(m)))
  [3.161804]

  [3.161837]
  + Ok((n, Some(hash), m))
• replacement in libpijul/src/pristine/mod.rs at line 392
  [3.40230]→[3.40230:40252](∅→∅)
  − ) -> Option<Merkle> {
  [3.40230]

  [3.40252]
  + ) -> Merkle {
• edit in libpijul/src/pristine/mod.rs at line 396
  [3.40357]

  [3.40357]
  + .unwrap_or(Merkle::zero())
• replacement in libpijul/src/lib.rs at line 405
  [3.730331]→[3.60805:60898](∅→∅)
  − fn current_state(&self, channel: &pristine::Channel<Self>) -> Option<pristine::Merkle> {
  [3.730331]

  [3.60898]
  + fn current_state(&self, channel: &pristine::Channel<Self>) -> pristine::Merkle {