Prepare to deprecate support for remote plugins

Neovim plans to deprecate remote plugins as described at
neovim/neovim#27949.

This commit removes references to remote plugins from all directories
except nvim/plugin.

We will wait for the completion of neovim/neovim#27949
before marking the `github.com/go-client/nvim/plugin` package as deprecated.

Author: garyburd

README.md

@@ -4,70 +4,7 @@
 [![Github Actions][Github Actions Badge]][Github Actions]
 [![codecov.io][codecov-badge]][codecov]
 
-Neovim/go-client is a [Neovim](https://neovim.io/) client and plugin host for [Go](https://golang.org/).
-
-This example plugin adds the Hello command to Nvim.
-
-```go
-package main
-
-import (
-    "strings"
-    "github.com/neovim/go-client/nvim/plugin"
-)
-
-func hello(args []string) (string, error) {
-    return "Hello " + strings.Join(args, " "), nil
-}
-
-func main() {
-    plugin.Main(func(p *plugin.Plugin) error {
-        p.HandleFunction(&plugin.FunctionOptions{Name: "Hello"}, hello)
-            return nil
-    })
-}
-```
-
-Build the program with the [go tool](https://golang.org/cmd/go/) to an
-executable named `hello`. Ensure that the executable is in a directory in
-the `PATH` environment variable.
-
-```go
-// Use the `go build` command to generate an executable.
-// To ensure this "hello" executable is on your path,
-// you can move "hello" to your $GOPATH/bin directory
-// or add the current directory to the `PATH` environment variable.
-go build -o hello
-```
-
-Add the following plugin to Nvim:
-
-```vim
-if exists('g:loaded_hello')
-    finish
-endif
-let g:loaded_hello = 1
-
-function! s:Requirehello(host) abort
-    " 'hello' is the binary created by compiling the program above.
-    return jobstart(['hello'], {'rpc': v:true})
-endfunction
-
-call remote#host#Register('hello', 'x', function('s:Requirehello'))
-" The following lines are generated by running the program
-" command line flag --manifest hello
-call remote#host#RegisterPlugin('hello', '0', [
-    \ {'type': 'function', 'name': 'Hello', 'sync': 1, 'opts': {}},
-    \ ])
-
-" vim:ts=4:sw=4:et
-```
-
-Start Nvim and run the following command:
-
-```vim
-:echo Hello('world')
-```
+Neovim/go-client is a [Neovim](https://neovim.io/) client for [Go](https://golang.org/).
 
 Release
 -------

nvim/doc.go

@@ -1,10 +1,7 @@
 // Package nvim implements a Nvim client.
 //
-// See the ./plugin package for additional functionality required for writing
-// Nvim plugins.
-//
 // The Nvim type implements the client. To connect to a running instance of
-// Nvim, create a *Nvim value using the Dial or NewChildProcess functions.
+// Nvim, create a *Nvim value using the New, Dial or NewChildProcess functions.
 // Call the Close() method to release the resources used by the client.
 //
 // Use the Batch type to execute a sequence of Nvim API calls atomically. The

nvim/nvim.go

@@ -103,9 +103,6 @@ func (v *Nvim) ExitCode() int {
 //
 // The application must call Serve() to handle RPC requests and responses.
 //
-// New is a low-level function. Most applications should use NewChildProcess,
-// Dial or the ./plugin package.
-//
 //	:help rpc-connecting
 func New(r io.Reader, w io.Writer, c io.Closer, logf func(string, ...interface{})) (*Nvim, error) {
 	ep, err := rpc.NewEndpoint(r, w, c, rpc.WithLogf(logf), withExtensions())
@@ -354,8 +351,6 @@ func Dial(address string, options ...DialOption) (*Nvim, error) {
 //	:help rpcrequest()
 //	:help rpcnotify()
 //
-// Plugin applications should use the Handler* methods in the ./plugin package
-// to register handlers instead of this method.
 func (v *Nvim) RegisterHandler(method string, fn interface{}) error {
 	var args []interface{}
 	t := reflect.TypeOf(fn)

nvim/plugin/README.md

@@ -0,0 +1,74 @@
+Status
+------
+
+This package will be deprecated when Neovim [removes the concept of
+remote plugins](https://github.com/neovim/neovim/issues/27949).  
+
+
+Example
+-------
+
+This example plugin adds the Hello command to Nvim.
+
+```go
+package main
+
+import (
+    "strings"
+    "github.com/neovim/go-client/nvim/plugin"
+)
+
+func hello(args []string) (string, error) {
+    return "Hello " + strings.Join(args, " "), nil
+}
+
+func main() {
+    plugin.Main(func(p *plugin.Plugin) error {
+        p.HandleFunction(&plugin.FunctionOptions{Name: "Hello"}, hello)
+            return nil
+    })
+}
+```
+
+Build the program with the [go tool](https://golang.org/cmd/go/) to an
+executable named `hello`. Ensure that the executable is in a directory in
+the `PATH` environment variable.
+
+```bash
+// Use the `go build` command to generate an executable.
+// To ensure this "hello" executable is on your path,
+// you can move "hello" to your $GOPATH/bin directory
+// or add the current directory to the `PATH` environment variable.
+go build -o hello
+```
+
+Add the following plugin to Nvim:
+
+```vim
+if exists('g:loaded_hello')
+    finish
+endif
+let g:loaded_hello = 1
+
+function! s:Requirehello(host) abort
+    " 'hello' is the binary created by compiling the program above.
+    return jobstart(['hello'], {'rpc': v:true})
+endfunction
+
+call remote#host#Register('hello', 'x', function('s:Requirehello'))
+" The following lines are generated by running the program
+" command line flag --manifest hello
+call remote#host#RegisterPlugin('hello', '0', [
+    \ {'type': 'function', 'name': 'Hello', 'sync': 1, 'opts': {}},
+    \ ])
+
+" vim:ts=4:sw=4:et
+```
+
+Start Nvim and run the following command:
+
+```vim
+:echo Hello('world')
+```
+
+