docs: update readme

Author: smjonas

README.md

@@ -7,15 +7,13 @@ Text editing in Neovim with immediate visual feedback: view the effects of any c
 <p><sub>Theme: <a href="https://github.com/folke/tokyonight.nvim">tokyonight.nvim</a></sub></p>
 
 ## :sparkles: Motivation and Features
-In version 0.8, Neovim has introduced the `command-preview` feature.
-Contrary to what "command preview" suggests, previewing any given
-command does not work out of the box: you need to manually update the buffer text and set
-highlights *for every command*.
-
-This plugin tries to change that: it provides a **simple API for creating previewable commands**
-in Neovim. Just specify the command you want to run and live-command will do all the
-work for you. This includes viewing **individual insertions, changes and deletions** as you
-type.
+In Neovim version 0.8, the `command-preview` feature has been introduced.
+Despite its name, it does not enable automatic previewing of any command.
+Instead, users must manually update the buffer text and set highlights *for each command*.
+
+This plugin aims to address this issue by offering a **simple API for creating previewable commands**
+in Neovim. Simply provide the command you want to preview and live-command will do all the
+work for you. This includes viewing **individual insertions, changes and deletions** as you type.
 
 ## Requirements
 Neovim 0.8+

migrate_to_v2.md

@@ -0,0 +1,60 @@
+# Migration to v2.0
+This is a guide for users that want to migrate to version `2.0` of `live-command`.
+If you want to stay on the previous major version, you can pin the plugin to the tag [`1.x`](https://github.com/smjonas/live-command.nvim/releases/tag/1.x).
+
+## What has changed in version 2.0?
+Version 2.0 is a rewrite of the plugin for better maintainability and future extensibility.
+It simplifies the user-facing API while improving the architecture of the plugin and adding a new `:Preview` command.
+
+**Breaking change**:
+- Custom command specifications now only consist of a `cmd` value (a string); `args`
+  and `range` have been removed. See [next section](#how-can-i-migrate-from-older-versions).
+
+**New feature**:
+- New generic `:Preview` command that allows to preview any command without having to
+  define it in the configuration. This is useful to test out the capabilities of
+  `live-command` or if you don't use a command as often to warrant a separate user command.
+  The command itself does not take a range or count. Example: `:Preview '<,'>norm daw`
+  previews deletion of the first word of the selected lines.
+
+## How can I migrate from older versions?
+In versions `1.x`, the following example was provided showing how to preview the results of a macro:
+```lua
+local commands = {
+  Reg = {
+    cmd = "norm",
+    -- This will transform ":5Reg a" into ":norm 5@a"
+    args = function(opts)
+      return (opts.count == -1 and "" or opts.count) .. "@" .. opts.args
+    end,
+    range = "",
+  },
+}
+```
+In version `2.0`, you have two options:
+1. Define a command `Norm = { cmd = "norm" }` and use it as `:Norm <count>@<register>` (e.g., `:Norm 5@a` to apply macro stored in register `a` five times).
+2. Define a custom `:Reg` user command like this that works just like the old version:
+
+<details>
+  <summary>View code</summary>
+
+```lua
+-- Turns ":5Reg a" into ":norm 5@a"
+local function get_command_string(cmd)
+  local get_range_string = require("live-command").get_range_string
+  local args = (cmd.count == -1 and "" or cmd.count) .. "@" .. cmd.args
+  return get_range_string(cmd) .. "norm " .. args
+end
+
+vim.api.nvim_create_user_command("Reg", function(cmd)
+  vim.cmd(get_command_string(cmd))
+end, {
+  nargs = "?",
+  range = true,
+  preview = function(cmd, preview_ns, preview_buf)
+    local cmd_to_preview = get_command_string(cmd)
+    return require("live-command").preview_callback(cmd_to_preview, preview_ns, preview_buf)
+  end
+})
+```
+</details>