Flushing the futures pipeline when downloading over HTTP(S)

Dependencies

• [2] IQ4FCHPZ HTTP connections: pooling + retry on error
• [3] SXEYMYF7 Fixing the bad changes in history (unfortunately, by rebooting).
• [4] X6YFD4WV Do not download changes if we already have them
• [5] BZSC7VMY address clippy lints
• [6] UDHP4ZVB Fixing SSH asynchronicity issues
• [7] WLUID7NA Do not block when downloading more than 100 changes over SSH
• [*] FBXYP7QM Forgot to add remote::http

Change contents

• replacement in pijul/src/remote/ssh.rs at line 448
  [3.4784]→[3.4784:4840](∅→∅)
  − path.set_extension("");
  [3.4784]

  [3.4840]
  + path.set_extension("tmp");
• replacement in pijul/src/remote/ssh.rs at line 786
  [3.46548]→[3.46548:46580](∅→∅)
  − path.set_extension("");
  [3.46548]

  [3.9044]
  + path.set_extension("tmp");
• edit in pijul/src/remote/http.rs at line 107
  [2.2118]

  [9.1349]
  + }

  + for f in 0..POOL_SIZE {

  + if let Some(t) = pool[(cur + f) % POOL_SIZE].take() {

  + let c = t.await??;

  + if send.send(c).await.is_err() {

  + debug!("err for {:?}", c);

  + progress.abandon();

  + break;

  + }

  + }