Provide update_events as an alias for updateevents.

`updateevents` will continue working, but `update_events` is in line
with other config-keys, so recommend using that.

Examples/snippets.lua

@@ -26,7 +26,7 @@ local conds = require("luasnip.extras.expand_conditions")
 ls.config.set_config({
 	history = true,
 	-- Update more often, :h events for more info.
-	updateevents = "TextChanged,TextChangedI",
+	update_events = "TextChanged,TextChangedI",
 	-- Snippets aren't automatically removed if their text is deleted.
 	-- `delete_check_events` determines on which events (:h events) a check for
 	-- deleted snippets is performed.

README.md

@@ -205,7 +205,7 @@ The [Wiki](https://github.com/L3MON4D3/LuaSnip/wiki) contains some pretty useful
 
 # Config
 - `history`: If true, Snippets that were exited can still be jumped back into. As Snippets are not removed when their text is deleted, they have to be removed manually via `LuasnipUnlinkCurrent` if `delete_check_events` is not enabled (set to eg. `'TextChanged'`).
-- `updateevents`: Choose which events trigger an update of the active nodes' dependents. Default is just `'InsertLeave'`, `'TextChanged,TextChangedI'` would update on every change.
+- `update_events`: Choose which events trigger an update of the active nodes' dependents. Default is just `'InsertLeave'`, `'TextChanged,TextChangedI'` would update on every change.
 - `region_check_events`: Events on which to leave the current snippet if the cursor is outside its' 'region'. Disabled by default, `'CursorMoved'`, `'CursorHold'` or `'InsertEnter'` seem reasonable.
 - `delete_check_events`: When to check if the current snippet was deleted, and if so, remove it from the history. Off by default, `'TextChanged'` (perhaps `'InsertLeave'`, to react to changes done in Insert mode) should work just fine (alternatively, this can also be mapped using `<Plug>luasnip-delete-check`). 
 - `store_selection_keys`: Mapping for populating `TM_SELECTED_TEXT` and related variables (not set by default).

lua/luasnip/config.lua

@@ -5,7 +5,7 @@ local session = require("luasnip.session")
 
 local defaults = {
 	history = false,
-	updateevents = "InsertLeave",
+	update_events = "InsertLeave",
 	-- see :h User, event should never be triggered(except if it is `doautocmd`'d)
 	region_check_events = "User None",
 	delete_check_events = "User None",
@@ -120,6 +120,12 @@ c = {
 		)
 		ext_util.child_extend(user_config.ext_opts, conf.ext_opts)
 
+		-- use value from update_events, then updateevents.
+		-- also nil updateevents, don't spill it into the main config.
+		user_config.update_events = user_config.update_events
+			or user_config.updateevents
+		user_config.updateevents = nil
+
 		for k, v in pairs(user_config) do
 			conf[k] = v
 		end
@@ -149,7 +155,7 @@ c = {
 		augroup END
 		]],
 				session.config.delete_check_events,
-				session.config.updateevents,
+				session.config.update_events,
 				session.config.region_check_events
 			)
 		)