Add podman farm update command

Podman farm update allows users to update a farm by addig
connections, removing connections, or changing the default farm.

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

cmd/podman/farm/update.go

@@ -0,0 +1,109 @@
+package farm
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/containers/common/pkg/completion"
+	"github.com/containers/common/pkg/config"
+	"github.com/containers/podman/v4/cmd/podman/common"
+	"github.com/containers/podman/v4/cmd/podman/registry"
+	"github.com/spf13/cobra"
+)
+
+var (
+	farmUpdateDescription = `Update an existing farm by adding a connection, removing a connection, or changing it to the default farm.`
+	updateCommand         = &cobra.Command{
+		Use:               "update [options] FARM",
+		Short:             "Update an existing farm",
+		Long:              farmUpdateDescription,
+		RunE:              farmUpdate,
+		Args:              cobra.ExactArgs(1),
+		ValidArgsFunction: common.AutoCompleteFarms,
+		Example: `podman farm update --add con1 farm1
+	podman update --remove con2 farm2
+	podman update --default farm3`,
+	}
+
+	// Temporary struct to hold cli values.
+	updateOpts = struct {
+		Add     []string
+		Remove  []string
+		Default bool
+	}{}
+)
+
+func init() {
+	registry.Commands = append(registry.Commands, registry.CliCommand{
+		Command: updateCommand,
+		Parent:  farmCmd,
+	})
+	flags := updateCommand.Flags()
+
+	addFlagName := "add"
+	flags.StringSliceVarP(&updateOpts.Add, addFlagName, "a", nil, "add system connection(s) to farm")
+	_ = updateCommand.RegisterFlagCompletionFunc(addFlagName, completion.AutocompleteNone)
+	removeFlagName := "remove"
+	flags.StringSliceVarP(&updateOpts.Remove, removeFlagName, "r", nil, "remove system connection(s) from farm")
+	_ = updateCommand.RegisterFlagCompletionFunc(removeFlagName, completion.AutocompleteNone)
+	defaultFlagName := "default"
+	flags.BoolVarP(&updateOpts.Default, defaultFlagName, "d", false, "set the given farm as the default farm")
+}
+
+func farmUpdate(cmd *cobra.Command, args []string) error {
+	farmName := args[0]
+
+	defChanged := cmd.Flags().Changed("default")
+
+	if len(updateOpts.Add) == 0 && len(updateOpts.Remove) == 0 && !defChanged {
+		return fmt.Errorf("nothing to update for farm %q, please use the --add, --remove, or --default flags to update a farm", farmName)
+	}
+
+	cfg, err := config.ReadCustomConfig()
+	if err != nil {
+		return err
+	}
+
+	if len(cfg.Farms.List) == 0 {
+		return errors.New("no farms are created at this time, there is nothing to update")
+	}
+
+	if defChanged {
+		// Change the default to the given farm if --default=true
+		if updateOpts.Default {
+			cfg.Farms.Default = farmName
+		} else {
+			// if --default=false, user doesn't want any farms to be default so clear the DefaultFarm
+			cfg.Farms.Default = ""
+		}
+	}
+
+	if val, ok := cfg.Farms.List[farmName]; ok {
+		cMap := make(map[string]int)
+		for _, c := range val {
+			cMap[c] = 0
+		}
+
+		for _, cRemove := range updateOpts.Remove {
+			delete(cMap, cRemove)
+		}
+
+		for _, cAdd := range updateOpts.Add {
+			if _, ok := cMap[cAdd]; !ok {
+				cMap[cAdd] = 0
+			}
+		}
+
+		updatedConnections := []string{}
+		for k := range cMap {
+			updatedConnections = append(updatedConnections, k)
+		}
+		cfg.Farms.List[farmName] = updatedConnections
+	}
+
+	if err := cfg.Write(); err != nil {
+		return err
+	}
+	fmt.Printf("Farm %q updated\n", farmName)
+	return nil
+}

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

@@ -0,0 +1,39 @@
+% podman-farm-update 1
+
+## NAME
+podman\-farm\-update - Update an existing farm
+
+## SYNOPSIS
+**podman farm update** [*options*] *name*
+
+## DESCRIPTION
+Update a farm by either adding connections to it, removing connections from it, or setting it as the new
+default farm.
+
+## OPTIONS
+
+#### **--add**, **-a**
+
+Add new connections to an existing farm. Multiple connections can be added at once.
+
+#### **--default**, **-d**
+
+Set the current farm as the default.
+
+#### **--remove**, **-r**
+
+Remove one or more connections from an existing farm.
+
+## EXAMPLE
+```
+$ podman farm update --add f35,f38 farm1
+
+$ podman farm update --remove f35 farm1
+
+$ podman farm update --default 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)s