hide() for simple commit-walk

[Byron]

The long version of this got lost in a gh tool hickup, so in short:

• have only three tests, but these are all that's needed to know it works.
  • it can probably use more to assure it works in conjunction with sorting, etc.,
    but maybe the code can be made so it can't be wrong.
• fully backwards compatible
• Using a graph data structure it might be possible to fully cache results and speed-up
  future walks.

Tasks

• "the" 3 tests
• implementation
• the same tests but with sorting enabled
• hookup to gix commit-graph list for perf testing
  • figure out a way to abort early (even if it means not handling certain special cases well, probably abort if there are only uninteresting)
• make available in gix

Performance

linux ( master) +798 -408 [!]
❯ hyperfine '/Users/byron/dev/github.com/Byron/gitoxide/target/release/gix commit-graph list -l v6.7..v6.8' 'git log v6.7..v6.8 --oneline'
Benchmark 1: /Users/byron/dev/github.com/Byron/gitoxide/target/release/gix commit-graph list -l v6.7..v6.8
  Time (mean ± σ):     277.0 ms ±   1.5 ms    [User: 261.2 ms, System: 12.7 ms]
  Range (min … max):   274.9 ms … 279.2 ms    10 runs

Benchmark 2: git log v6.7..v6.8 --oneline
  Time (mean ± σ):     267.4 ms ±   6.9 ms    [User: 235.1 ms, System: 28.5 ms]
  Range (min … max):   261.3 ms … 286.2 ms    11 runs

Summary
  git log v6.7..v6.8 --oneline ran
    1.04 ± 0.03 times faster than /Users/byron/dev/github.com/Byron/gitoxide/target/release/gix commit-graph list -l v6.7..v6.8

gitoxide ( hide) [$?⇕⇡4⇣3] took 41s
❯ hyperfine './target/release/gix commit-graph list -l v0.42.0..v0.44.0' 'git log --oneline v0.42.0..v0.44.0'
Benchmark 1: ./target/release/gix commit-graph list -l v0.42.0..v0.44.0
  Time (mean ± σ):       9.5 ms ±   1.2 ms    [User: 4.3 ms, System: 2.7 ms]
  Range (min … max):     8.0 ms …  15.8 ms    233 runs

Benchmark 2: git log --oneline v0.42.0..v0.44.0
  Time (mean ± σ):      14.2 ms ±   1.4 ms    [User: 7.1 ms, System: 5.2 ms]
  Range (min … max):    12.5 ms …  21.5 ms    138 runs

Summary
  ./target/release/gix commit-graph list -l v0.42.0..v0.44.0 ran
    1.50 ± 0.24 times faster than git log --oneline v0.42.0..v0.44.0