docs: Add generated argocd command docs (#4606)

tools/cmd-docs/main.go

@@ -0,0 +1,20 @@
+package main
+
+import (
+	"log"
+	"os"
+
+	"github.com/argoproj/argo-cd/cmd/argocd/commands"
+
+	"github.com/spf13/cobra/doc"
+)
+
+func main() {
+	// set HOME env var so that default values involve user's home directory do not depend on the running user.
+	os.Setenv("HOME", "/home/user")
+
+	err := doc.GenMarkdownTree(commands.NewCommand(), "./docs/user-guide/commands")
+	if err != nil {
+		log.Fatal(err)
+	}
+}