fix(vim.mpack): rename pack/unpack => encode/decode #16175

Problem:
1. "unpack" has an unrelated meaning in Lua:
   https://www.lua.org/manual/5.1/manual.html#pdf-unpack
2. We already have msgpackparse()/msgpackdump() and
   json_encode()/json_decode(), so introducing another name for the same
   thing is entropy.

Solution:
- Rename vim.mpack.pack/unpack => vim.mpack.encode/decode

Caveat:
This is incongruent with the `Unpacker` and `Packer` functions.
- It's probably too invasive to rename those.
- They also aren't part of our documented interface.
- This commit is "reversible" in the sense that we can always revert
  it and add `vim.mpack.encode/decode` as _aliases_ to
  `vim.mpack.pack/unpack`, at any time in the future, if we want
  stricter fidelity with upstream libmpack. Meanwhile,
  `vim.mpack.encode/decode` is currently the total _documented_
  interface of `vim.mpack`, so this change serves the purpose of
  consistent naming in the Nvim stdlib.

1 files changed, 6 insertions, 7 deletions

diff --git a/runtime/doc/lua.txt b/runtime/doc/lua.txt
index 877c838602..1e058874bd 100644
--- a/runtime/doc/lua.txt
+++ b/runtime/doc/lua.txt
@@ -698,15 +698,14 @@ vim.diff({a}, {b}, {opts})                                        *vim.diff()*
 ------------------------------------------------------------------------------
 VIM.MPACK                                                          *lua-mpack*
 
-The *vim.mpack* module provides packing and unpacking of lua objects to
-msgpack encoded strings. |vim.NIL| and |vim.empty_dict()| are supported.
+The *vim.mpack* module provides encoding and decoding of Lua objects to and
+from msgpack-encoded strings. Supports |vim.NIL| and |vim.empty_dict()|.
 
-vim.mpack.pack({obj})                                   *vim.mpack.pack*
-        Packs a lua object {obj} and returns the msgpack representation as
-        a string
+vim.mpack.encode({obj})                                 *vim.mpack.encode*
+        Encodes (or "packs") Lua object {obj} as msgpack in a Lua string.
 
-vim.mpack.unpack({str})                                 *vim.mpack.unpack*
-        Unpacks the msgpack encoded {str} and returns a lua object
+vim.mpack.decode({str})                                 *vim.mpack.decode*
+        Decodes (or "unpacks") the msgpack-encoded {str} to a Lua object.
 
 ------------------------------------------------------------------------------
 VIM                                                     *lua-builtin*