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/config/login.go

@@ -111,6 +111,25 @@ func GetLoginByToken(token string) *Login {
 	return nil
 }
 
+// GetLoginByHost finds a login by it's server URL
+func GetLoginByHost(host string) *Login {
+	err := loadConfig()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	for _, l := range config.Logins {
+		loginURL, err := url.Parse(l.URL)
+		if err != nil {
+			log.Fatal(err)
+		}
+		if loginURL.Host == host {
+			return &l
+		}
+	}
+	return nil
+}
+
 // DeleteLogin delete a login by name from config
 func DeleteLogin(name string) error {
 	var idx = -1