fix(api): mark nvim__complete_set as experimental #28579

Problem:
nvim_complete_set was added in 5ed55ff14c8b7e346811cb6228bf63fb5106bae9
but needs more bake time.

Solution:
Rename it, mark it as experimental.

2 files changed, 7 insertions, 9 deletions

diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index e4e4ae29f2..8458611ee8 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -2282,20 +2282,18 @@ void nvim_error_event(uint64_t channel_id, Integer lvl, String data)
   ELOG("async error on channel %" PRId64 ": %s", channel_id, data.size ? data.data : "");
 }
 
-/// Set info for the completion candidate index.
-/// if the info was shown in a window, then the
-/// window and buffer ids are returned for further
-/// customization. If the text was not shown, an
-/// empty dict is returned.
+/// EXPERIMENTAL: this api may change in the future.
 ///
-/// @param index  the completion candidate index
+/// Sets info for the completion item at the given index. If the info text was shown in a window,
+/// returns the window and buffer ids, or empty dict if not shown.
+///
+/// @param index  Completion candidate index
 /// @param opts   Optional parameters.
 ///       - info: (string) info text.
 /// @return Dictionary containing these keys:
 ///       - winid: (number) floating window id
 ///       - bufnr: (number) buffer id in floating window
-Dictionary nvim_complete_set(Integer index, Dict(complete_set) *opts, Arena *arena)
-  FUNC_API_SINCE(12)
+Dictionary nvim__complete_set(Integer index, Dict(complete_set) *opts, Arena *arena)
 {
   Dictionary rv = arena_dict(arena, 2);
   if (HAS_KEY(opts, complete_set, info)) {
diff --git a/src/nvim/popupmenu.c b/src/nvim/popupmenu.c
index f2b8e85b8f..0a8842a136 100644
--- a/src/nvim/popupmenu.c
+++ b/src/nvim/popupmenu.c
@@ -732,7 +732,7 @@ static void pum_adjust_info_position(win_T *wp, int height, int width)
   win_config_float(wp, wp->w_config);
 }
 
-/// Used for nvim_complete_set
+/// Used for nvim__complete_set
 ///
 /// @param selected the selected compl item.
 /// @parma info     Info string.