Fix options of git subcommand

Dependencies

• [2] BXD3IQYN Fixing --features git
• [3] KWAMD2KR A few fixes in the documentation comments
• [4] AXVPNZ2N commands/git: fix imports
• [5] SXEYMYF7 Fixing the bad changes in history (unfortunately, by rebooting).
• [6] L4JXJHWX pijul/*: reorganize imports and remove extern crate
• [7] I52XSRUH Massive cleanup, and simplification

Change contents

• replacement in pijul/src/commands/git.rs at line 7
  [4.2237]→[4.0:16](∅→∅)
  − use clap::Clap;
  [4.2237]

  [2.0]
  + use clap::{ArgSettings, Clap};
• replacement in pijul/src/commands/git.rs at line 20
  [3.1785]→[3.1785:1844](∅→∅)
  − #[clap(long = "stats", setting = AppSettings::Hidden)]
  [3.1785]

  [4.137505]
  + #[clap(long = "stats", setting = ArgSettings::Hidden)]
• replacement in pijul/src/commands/git.rs at line 23
  [3.1895]→[3.1895:1959](∅→∅)
  − #[clap(default_value = "0", setting = AppSettings::Hidden)]
  [3.1895]

  [4.137602]
  + #[clap(default_value = "0", setting = ArgSettings::Hidden)]