add docs for kpt alpha rpkg update (#3747)

commands/alpha/rpkg/update/command.go

@@ -18,6 +18,7 @@ import (
 	"context"
 	"fmt"
 
+	"github.com/GoogleContainerTools/kpt/internal/docs/generated/rpkgdocs"
 	"github.com/GoogleContainerTools/kpt/internal/errors"
 	"github.com/GoogleContainerTools/kpt/internal/util/porch"
 	porchapi "github.com/GoogleContainerTools/kpt/porch/api/porch/v1alpha1"
@@ -46,6 +47,9 @@ func newRunner(ctx context.Context, rcg *genericclioptions.ConfigFlags) *runner
 		Use:     "update SOURCE_PACKAGE",
 		PreRunE: r.preRunE,
 		RunE:    r.runE,
+		Short:   rpkgdocs.UpdateShort,
+		Long:    rpkgdocs.UpdateShort + "\n" + rpkgdocs.UpdateLong,
+		Example: rpkgdocs.UpdateExamples,
 		Hidden:  porch.HidePorchCommands,
 	}
 	r.Command.Flags().StringVar(&r.revision, "revision", "", "Revision of the upstream package to update to.")

site/reference/cli/alpha/rpkg/update/README.md

@@ -0,0 +1,73 @@
+---
+title: "`clone`"
+linkTitle: "clone"
+type: docs
+description: >
+Update a downstream package revision to a more recent revision of its upstream package.
+---
+
+<!--mdtogo:Short
+    Update a downstream package revision to a more recent revision of its upstream package.
+-->
+
+`update` performs a kpt pkg update on an existing downstream package revision.
+
+### Synopsis
+
+<!--mdtogo:Long-->
+
+```
+kpt alpha rpkg update PACKAGE_REV_NAME [flags]
+```
+
+#### Args
+
+```
+PACKAGE_REV_NAME:
+The target downstream package revision to be updated.
+
+```
+
+#### Flags
+
+```
+--revision
+The revision number of the upstream kpt package that the target
+downstream package (PACKAGE_REV_NAME) should be updated to. With
+this flag, you can only specify one target downstream package.
+
+--discover
+If set, list packages revisions that need updates rather than
+performing an update. Must be one of 'upstream' or 'downstream'. If
+set to 'upstream', this will list downstream package revisions that
+have upstream updates available. If set to 'downstream', this will list
+upstream package revisions whose downstream package revisions need
+to be updated. You can optionally pass in package revision names as arguments
+in order to just list updates for those package revisions, or you can
+pass in no arguments in order to list available updates for all package
+revisions.
+
+```
+
+<!--mdtogo-->
+
+### Examples
+
+<!--mdtogo:Examples-->
+
+```shell
+# update deployment-e982b2196b35a4f5e81e92f49a430fe463aa9f1a package to v3 of its upstream
+$ kpt alpha rpkg update deployment-e982b2196b35a4f5e81e92f49a430fe463aa9f1a --revision=v3
+```
+
+```shell
+# see available upstream updates for all your downstream packages
+$ kpt alpha rpkg update --discover=upstream
+```
+
+```shell
+# see available updates for any downstream packages that were created from the upstream blueprints-e982b2196b35a4f5e81e92f49a430fe463aa9f1a package
+$ kpt alpha rpkg update --discover=downstream blueprints-e982b2196b35a4f5e81e92f49a430fe463aa9f1a
+```
+
+<!--mdtogo-->