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>

cmd/clone.go

@@ -0,0 +1,89 @@
+// Copyright 2021 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 cmd
+
+import (
+	"fmt"
+
+	"code.gitea.io/tea/cmd/flags"
+	"code.gitea.io/tea/modules/config"
+	"code.gitea.io/tea/modules/context"
+	"code.gitea.io/tea/modules/git"
+	"code.gitea.io/tea/modules/interact"
+	"code.gitea.io/tea/modules/task"
+	"code.gitea.io/tea/modules/utils"
+
+	"github.com/urfave/cli/v2"
+)
+
+// CmdRepoClone represents a sub command of repos to create a local copy
+var CmdRepoClone = cli.Command{
+	Name:    "clone",
+	Aliases: []string{"C"},
+	Usage:   "Clone a repository locally",
+	Description: `Clone a repository locally, without a local git installation required.
+The repo slug can be specified in different formats:
+	gitea/tea
+	tea
+	gitea.com/gitea/tea
+	git@gitea.com:gitea/tea
+	https://gitea.com/gitea/tea
+	ssh://gitea.com:22/gitea/tea
+When a host is specified in the repo-slug, it will override the login specified with --login.
+	`,
+	Category:  catHelpers,
+	Action:    runRepoClone,
+	ArgsUsage: "<repo-slug> [target dir]",
+	Flags: []cli.Flag{
+		&cli.IntFlag{
+			Name:    "depth",
+			Aliases: []string{"d"},
+			Usage:   "num commits to fetch, defaults to all",
+		},
+		&flags.LoginFlag,
+	},
+}
+
+func runRepoClone(cmd *cli.Context) error {
+	ctx := context.InitCommand(cmd)
+
+	args := ctx.Args()
+	if args.Len() < 1 {
+		return cli.ShowCommandHelp(cmd, "clone")
+	}
+	dir := args.Get(1)
+
+	var (
+		login *config.Login = ctx.Login
+		owner string        = ctx.Login.User
+		repo  string
+	)
+
+	// parse first arg as repo specifier
+	repoSlug := args.Get(0)
+	url, err := git.ParseURL(repoSlug)
+	if err != nil {
+		return err
+	}
+
+	owner, repo = utils.GetOwnerAndRepo(url.Path, login.User)
+	if url.Host != "" {
+		login = config.GetLoginByHost(url.Host)
+		if login == nil {
+			return fmt.Errorf("No login configured matching host '%s', run `tea login add` first", url.Host)
+		}
+	}
+
+	_, err = task.RepoClone(
+		dir,
+		login,
+		owner,
+		repo,
+		interact.PromptPassword,
+		ctx.Int("depth"),
+	)
+
+	return err
+}