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/git/url_test.go

@@ -0,0 +1,56 @@
+// Copyright 2019 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package git
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestParseUrl(t *testing.T) {
+	u, err := ParseURL("ssh://git@gitea.com:3000/gitea/tea")
+	assert.NoError(t, err)
+	assert.Equal(t, "gitea.com:3000", u.Host)
+	assert.Equal(t, "ssh", u.Scheme)
+	assert.Equal(t, "/gitea/tea", u.Path)
+
+	u, err = ParseURL("https://gitea.com/gitea/tea")
+	assert.NoError(t, err)
+	assert.Equal(t, "gitea.com", u.Host)
+	assert.Equal(t, "https", u.Scheme)
+	assert.Equal(t, "/gitea/tea", u.Path)
+
+	u, err = ParseURL("git@gitea.com:gitea/tea")
+	assert.NoError(t, err)
+	assert.Equal(t, "gitea.com", u.Host)
+	assert.Equal(t, "ssh", u.Scheme)
+	assert.Equal(t, "/gitea/tea", u.Path)
+
+	u, err = ParseURL("gitea.com/gitea/tea")
+	assert.NoError(t, err)
+	assert.Equal(t, "gitea.com", u.Host)
+	assert.Equal(t, "https", u.Scheme)
+	assert.Equal(t, "/gitea/tea", u.Path)
+
+	u, err = ParseURL("foo/bar")
+	assert.NoError(t, err)
+	assert.Equal(t, "", u.Host)
+	assert.Equal(t, "", u.Scheme)
+	assert.Equal(t, "foo/bar", u.Path)
+
+	u, err = ParseURL("/foo/bar")
+	assert.NoError(t, err)
+	assert.Equal(t, "", u.Host)
+	assert.Equal(t, "https", u.Scheme)
+	assert.Equal(t, "/foo/bar", u.Path)
+
+	// this case is unintuitive, but to ambiguous to be handled differently
+	u, err = ParseURL("gitea.com")
+	assert.NoError(t, err)
+	assert.Equal(t, "", u.Host)
+	assert.Equal(t, "", u.Scheme)
+	assert.Equal(t, "gitea.com", u.Path)
+}