support create agit flow pull request (#867)

while looks the alibaba has not maintain
[`git-repo-go`](https://github.com/alibaba/git-repo-go/)
tool, to make agit flow pull requst can be create quickly.
add creating agit flow pull request feature
in tea tool

example:

```SHELL
tea pulls create --agit --remote=origin --topic=test-topic
--title="hello world" --description="test1
test 2
test 3"
```

Signed-off-by: a1012112796 <1012112796@qq.com>
Reviewed-on: https://gitea.com/gitea/tea/pulls/867
Co-authored-by: a1012112796 <1012112796@qq.com>
Co-committed-by: a1012112796 <1012112796@qq.com>

cmd/pulls/create.go

@@ -37,6 +37,14 @@ var CmdPullsCreate = cli.Command{
 			Usage:   "Enable maintainers to push to the base branch of created pull",
 			Value:   true,
 		},
+		&cli.BoolFlag{
+			Name:  "agit",
+			Usage: "Create an agit flow pull request",
+		},
+		&cli.StringFlag{
+			Name:  "topic",
+			Usage: "Topic name for agit flow pull request",
+		},
 	}, flags.IssuePRCreateFlags...),
 }
 
@@ -61,6 +69,18 @@ func runPullsCreate(_ stdctx.Context, cmd *cli.Command) error {
 		return err
 	}
 
+	if ctx.Bool("agit") {
+		return task.CreateAgitFlowPull(
+			ctx,
+			ctx.String("remote"),
+			ctx.String("head"),
+			ctx.String("base"),
+			ctx.String("topic"),
+			opts,
+			interact.PromptPassword,
+		)
+	}
+
 	var allowMaintainerEdits *bool
 	if ctx.IsSet("allow-maintainer-edits") {
 		allowMaintainerEdits = gitea.OptionalBool(ctx.Bool("allow-maintainer-edits"))