breakup v2 documentation

docs/v2/getting-started.md

@@ -0,0 +1,56 @@
+One of the philosophies behind cli is that an API should be playful and full of
+discovery. So a cli app can be as little as one line of code in `main()`.
+
+<!-- {
+  "args": ["&#45;&#45;help"],
+  "output": "A new cli application"
+} -->
+```go
+package main
+
+import (
+	"os"
+
+	"github.com/urfave/cli/v2"
+)
+
+func main() {
+	(&cli.App{}).Run(os.Args)
+}
+```
+
+This app will run and show help text, but is not very useful. Let's give an
+action to execute and some help documentation:
+
+<!-- {
+  "output": "boom! I say!"
+} -->
+```go
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+
+	"github.com/urfave/cli/v2"
+)
+
+func main() {
+	app := &cli.App{
+		Name:  "boom",
+		Usage: "make an explosive entrance",
+		Action: func(*cli.Context) error {
+			fmt.Println("boom! I say!")
+			return nil
+		},
+	}
+
+	if err := app.Run(os.Args); err != nil {
+		log.Fatal(err)
+	}
+}
+```
+
+Running this already gives you a ton of functionality, plus support for things
+like subcommands and flags, which are covered below.