cli: add complete support for offline signing, fix #2662

See documentation update for an example. Some code is made generic as well,
GetCompleteTransaction can now be used directly on ParameterContext.

cli/util/send.go

@@ -0,0 +1,42 @@
+package util
+
+import (
+	"fmt"
+
+	"github.com/nspcc-dev/neo-go/cli/options"
+	"github.com/nspcc-dev/neo-go/cli/paramcontext"
+	"github.com/urfave/cli"
+)
+
+func sendTx(ctx *cli.Context) error {
+	args := ctx.Args()
+	if len(args) == 0 {
+		return cli.NewExitError("missing input file", 1)
+	} else if len(args) > 1 {
+		return cli.NewExitError("only one input file is accepted", 1)
+	}
+
+	pc, err := paramcontext.Read(args[0])
+	if err != nil {
+		return cli.NewExitError(err, 1)
+	}
+
+	tx, err := pc.GetCompleteTransaction()
+	if err != nil {
+		return cli.NewExitError(fmt.Errorf("failed to complete transaction: %w", err), 1)
+	}
+
+	gctx, cancel := options.GetTimeoutContext(ctx)
+	defer cancel()
+
+	c, err := options.GetRPCClient(gctx, ctx)
+	if err != nil {
+		return cli.NewExitError(fmt.Errorf("failed to create RPC client: %w", err), 1)
+	}
+	res, err := c.SendRawTransaction(tx)
+	if err != nil {
+		return cli.NewExitError(fmt.Errorf("failed to submit transaction to RPC node: %w", err), 1)
+	}
+	fmt.Fprintln(ctx.App.Writer, res.StringLE())
+	return nil
+}