Add podman farm create command

The podman farm create command allows users to create
farms from the avaiable podman system connections.

Signed-off-by: Urvashi Mohnani <umohnani@redhat.com>

cmd/podman/farm/create.go

@@ -0,0 +1,80 @@
+package farm
+
+import (
+	"fmt"
+
+	"github.com/containers/common/pkg/completion"
+	"github.com/containers/common/pkg/config"
+	"github.com/containers/podman/v4/cmd/podman/registry"
+	"github.com/containers/podman/v4/pkg/util"
+	"github.com/spf13/cobra"
+)
+
+var (
+	farmCreateDescription = `Create a new farm with connections added via podman system connection add.
+
+	The "podman system connection add --farm" command can be used to add a new connection to a new or existing farm.`
+
+	createCommand = &cobra.Command{
+		Use:               "create [options] NAME [CONNECTIONS...]",
+		Args:              cobra.MinimumNArgs(1),
+		Short:             "Create a new farm",
+		Long:              farmCreateDescription,
+		RunE:              create,
+		ValidArgsFunction: completion.AutocompleteNone,
+		Example: `podman farm create myfarm connection1
+  podman farm create myfarm`,
+	}
+)
+
+func init() {
+	registry.Commands = append(registry.Commands, registry.CliCommand{
+		Command: createCommand,
+		Parent:  farmCmd,
+	})
+}
+
+func create(cmd *cobra.Command, args []string) error {
+	farmName := args[0]
+	connections := args[1:]
+
+	cfg, err := config.ReadCustomConfig()
+	if err != nil {
+		return err
+	}
+
+	if _, ok := cfg.Farms.List[farmName]; ok {
+		// if farm exists return an error
+		return fmt.Errorf("farm with name %q already exists", farmName)
+	}
+
+	// Can create an empty farm without any connections
+	if len(connections) == 0 {
+		cfg.Farms.List[farmName] = []string{}
+	}
+
+	for _, c := range connections {
+		if _, ok := cfg.Engine.ServiceDestinations[c]; ok {
+			if util.StringInSlice(c, cfg.Farms.List[farmName]) {
+				// Don't add duplicate connections to a farm
+				continue
+			}
+			cfg.Farms.List[farmName] = append(cfg.Farms.List[farmName], c)
+		} else {
+			return fmt.Errorf("cannot create farm, %q is not a system connection", c)
+		}
+	}
+
+	// If this is the first farm being created, set it as the default farm
+	if len(cfg.Farms.List) == 1 {
+		cfg.Farms.Default = farmName
+	}
+
+	err = cfg.Write()
+	if err != nil {
+		return err
+	}
+
+	fmt.Printf("Farm %q created\n", farmName)
+	return nil
+}

docs/source/markdown/podman-farm-create.1.md

@@ -0,0 +1,29 @@
+% podman-farm-create 1
+
+## NAME
+podman\-farm\-create - Create a new farm
+
+## SYNOPSIS
+**podman farm create** [*options*] *name* [*connections*]
+
+## DESCRIPTION
+Create a new farm with connections that podman knows about which were added via the
+*podman system connection add* command.
+
+An empty farm can be created without adding any connections to it. Add or remove
+connections from a farm via the *podman farm update* command.
+
+## OPTIONS
+
+## EXAMPLE
+
+```
+$ podman farm create farm1 f37 f38
+
+$ podman farm farm2
+```
+## SEE ALSO
+**[podman(1)](podman.1.md)**, **[podman-farm(1)](podman-farm.1.md)**
+
+## HISTORY
+July 2023, Originally compiled by Urvashi Mohnani (umohnani at redhat dot com)