Update doc on how to migrate away from chezmoi

docs/HOWTO.md

@@ -1396,6 +1396,22 @@ contents.
 
 ## Migrate away from chezmoi
 
-chezmoi creates regular files and directories - your home directory managed by
-chezmoi is exactly the same as if you were using no dotfile manager at all. Use
-your new dotfile manager's functionality for importing your existing dotfiles.
+chezmoi provides several mechanisms to help you move to an alternative dotfile
+manager (or even no dotfile manager at all) in the future:
+
+* chezmoi creates your dotfiles just as if you were not using a dotfile manager
+  at all. Your dotfiles are regular files, directories, and symlinks. You can
+  run [`chezmoi
+  purge`](https://github.com/twpayne/chezmoi/blob/master/docs/REFERENCE.md#purge)
+  to delete all traces of chezmoi and then, if you're migrating to a new dotfile
+  manager, then you can use whatever mechanism it provides to add your dotfiles
+  to your new system.
+* chezmoi has a [`chezmoi
+  archive`](https://github.com/twpayne/chezmoi/blob/master/docs/REFERENCE.md#archive)
+  command that generates a tarball of your dotfiles. You can replace the
+  contents of your dotfiles repo with the contents of the archive and you've
+  effectively immediately migrated away from chezmoi.
+* chezmoi has a [`chezmoi
+  dump`](https://github.com/twpayne/chezmoi/blob/master/docs/REFERENCE.md#dump-target)
+  command that dumps the interpreted (target) state in a machine-readable form,
+  so you can write scripts around chezmoi.