Add tea clone (#411)

Adds a new subcommand to clone repos:
```
tea clone --login try --depth 1 norwin/test
tea clone gitea/tea
tea clone noerw/tea           # will set up `master` to track `upstream` remote
tea clone try.gitea.io/noerw/test # will automatically set --login
```

This is just a replacement for `git clone` with small benefits:
- [x] does not depend on `git`, as tea ships with go-git
- [x] spares you typing of URLs and autoselects https/ssh based on your login config
- [x] forked repos: set up origin + upstream remote

Co-authored-by: Norwin <git@nroo.de>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>
Reviewed-on: https://gitea.com/gitea/tea/pulls/411
Reviewed-by: Andrew Thornton <art27@cantab.net>
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Norwin <noerw@noreply.gitea.io>
Co-committed-by: Norwin <noerw@noreply.gitea.io>

modules/task/pull_create.go

@@ -108,7 +108,7 @@ func GetDefaultPRHead(localRepo *local_git.TeaRepo) (owner, branch string, err e
 	if err != nil {
 		return
 	}
-	owner, _ = utils.GetOwnerAndRepo(strings.TrimLeft(url.Path, "/"), "")
+	owner, _ = utils.GetOwnerAndRepo(url.Path, "")
 	return
 }