remove disable_char_avail_for_testing()

test_cursor_func.vim hangs at the call to
disable_char_avail_for_testing(). The test does not actually need this
function (and it correctly fails if the fix from 7.4.1300 is reverted).
Given that disable_char_avail_for_testing is a gigantic hack, if we can
avoid it let's do so.

runtime/doc/eval.txt

@@ -1839,7 +1839,6 @@ dictwatcherdel( {dict}, {pattern}, {callback})
 did_filetype()			Number	TRUE if FileType autocommand event used
 diff_filler( {lnum})		Number	diff filler lines about {lnum}
 diff_hlID( {lnum}, {col})	Number	diff highlighting at {lnum}/{col}
-disable_char_avail_for_testing({expr})  none  test without typeahead
 empty( {expr})			Number	TRUE if {expr} is empty
 escape( {string}, {chars})	String	escape {chars} in {string} with '\'
 eval( {string})			any	evaluate {string} into its value
@@ -2868,13 +2867,6 @@ diff_hlID({lnum}, {col})				*diff_hlID()*
 		The highlight ID can be used with |synIDattr()| to obtain
 		syntax information about the highlighting.
 
-disable_char_avail_for_testing({expr})
-		When {expr} is 1 the internal char_avail() function will
-		return FALSE.  When {expr} is 0 the char_avail() function will
-		function normally.
-		Only use this for a test where typeahead causes the test not
-		to work.  E.g., to trigger the CursorMovedI autocommand event.
-
 empty({expr})						*empty()*
 		Return the Number 1 if {expr} is empty, zero otherwise.
 		A |List| or |Dictionary| is empty when it does not have any

src/nvim/eval.c

@@ -6708,7 +6708,6 @@ static struct fst {
   { "did_filetype",      0, 0, f_did_filetype },
   { "diff_filler",       1, 1, f_diff_filler },
   { "diff_hlID",         2, 2, f_diff_hlID },
-  { "disable_char_avail_for_testing", 1, 1, f_disable_char_avail_for_testing },
   { "empty",             1, 1, f_empty },
   { "escape",            2, 2, f_escape },
   { "eval",              1, 1, f_eval },
@@ -8604,15 +8603,6 @@ static void f_diff_hlID(typval_T *argvars, typval_T *rettv)
   rettv->vval.v_number = hlID == (hlf_T)0 ? 0 : (int)hlID;
 }
 
-//
-// "disable_char_avail_for_testing({expr})" function
-//
-static void f_disable_char_avail_for_testing(typval_T *argvars, typval_T *rettv)
-  FUNC_ATTR_NONNULL_ARG(1)
-{
-    disable_char_avail_for_testing = get_tv_number(&argvars[0]);
-}
-
 /*
  * "empty({expr})" function
  */

src/nvim/getchar.c

@@ -1562,11 +1562,6 @@ int char_avail(void)
 {
   int retval;
 
-  // When disable_char_avail_for_testing(1) was called pretend
-  // there is no typeahead
-  if (disable_char_avail_for_testing) {
-    return false;
-  }
   no_mapping++;
   retval = vpeekc();
   --no_mapping;

src/nvim/globals.h

@@ -1239,8 +1239,6 @@ EXTERN FILE *time_fd INIT(= NULL);  /* where to write startup timing */
 EXTERN int ignored;
 EXTERN char *ignoredp;
 
-EXTERN int  disable_char_avail_for_testing INIT(= 0);
-
 // If a msgpack-rpc channel should be started over stdin/stdout
 EXTERN bool embedded_mode INIT(= false);
 EXTERN Loop loop;

src/nvim/testdir/test_cursor_func.vim

@@ -44,9 +44,7 @@ func Test_curswant_with_autocommand()
   new
   call setline(1, ['func()', '{', '}', '----'])
   autocmd! CursorMovedI * call s:Highlight_Matching_Pair()
-  call disable_char_avail_for_testing(1)
   exe "normal! 3Ga\<Down>X\<Esc>"
-  call disable_char_avail_for_testing(0)
   call assert_equal('-X---', getline(4))
   autocmd! CursorMovedI *
   quit!

src/nvim/version.c

@@ -377,7 +377,7 @@ static int included_patches[] = {
   // 1303 NA
   // 1302 NA
   // 1301 NA
-  1300,
+  // 1300 NA
   // 1299 NA
   // 1298 NA
   // 1297 NA