Default to command-line git, instead of JGit

[eed3si9n]

Branching off from #243 (comment).

Let's default to using the command-line git instead of using an emulation via JGit.
There's been issued raised around the work tree support, and workarounds are proposed to automatically change the behavior around this #243, but my guess is that the need for JGit is limited to the default. The popularity of sbt-dynver sort of is an existential proof that most developers working on open source would have git installed on PATH.

[acyclic-ai]

+1, current depending egit is very old and doesn't support worktree.

Can't even switch to it:

/home/peng/git-release/__LEGACY/frameless/git.sbt:1: error: overloaded method value / with alternatives:
  (configAxis: sbt.ScopeAxis[sbt.ConfigKey])sbt.SlashSyntax.RichConfiguration <and>
  (c: sbt.librarymanagement.Configuration)sbt.SlashSyntax.RichConfiguration <and>
  (c: sbt.ConfigKey)sbt.SlashSyntax.RichConfiguration <and>
  (key: sbt.internal.util.AttributeKey[_])sbt.SlashSyntax.RichScope <and>
  [K](key: sbt.Scoped.ScopingSetting[K])K
 cannot be applied to (sbt.Def.Setting[_$2(in method $sbtdef)])
ThisBuild / useReadableConsoleGit := true
          ^
[error] Type error in expression
[warn] Project loading failed: (r)etry, (q)uit, (l)ast, or (i)gnore? (default: r)

(error observed at commit tribbloid/frameless@35726e2)

[mkurz]

@eed3si9n Please take a look at

• Prefer system git by default with fall back to JGit #382