patch 8.2.0637: incsearch highlighting does not work for ":sort!"

Problem:    Incsearch highlighting does not work for ":sort!".
Solution:   Skip over the exclamation point. (closes #5983)

src/ex_getln.c

@@ -249,7 +249,9 @@ do_incsearch_highlighting(int firstc, int *search_delim, incsearch_state_T *is_s
     }
     else if (STRNCMP(cmd, "sort", MAX(p - cmd, 3)) == 0)
     {
-	// skip over flags
+	// skip over ! and flags
+	if (*p == '!')
+	    p = skipwhite(p + 1);
 	while (ASCII_ISALPHA(*(p = skipwhite(p))))
 	    ++p;
 	if (*p == NUL)

src/testdir/dumps/Test_incsearch_sort_02.dump

@@ -0,0 +1,9 @@
+|a+0&#ffffff0|n|o|t|h|e|r| |o+1&&|n|e+0&&| |2| @56
+|t|h|a|t| |o+0&#ffff4012|n|e+0&#ffffff0| |3| @59
+|t|h|e| |o+0&#ffff4012|n|e+0&#ffffff0| |1| @60
+|~+0#4040ff13&| @68
+|~| @68
+|~| @68
+|~| @68
+|~| @68
+|:+0#0000000&|s|o|r|t|!| |/|o|n> @59

src/testdir/test_search.vim

@@ -1136,11 +1136,14 @@ func Test_incsearch_sort_dump()
   " the 'ambiwidth' check.
   sleep 100m
 
-  " Need to send one key at a time to force a redraw.
   call term_sendkeys(buf, ':sort ni u /on')
   call VerifyScreenDump(buf, 'Test_incsearch_sort_01', {})
   call term_sendkeys(buf, "\<Esc>")
 
+  call term_sendkeys(buf, ':sort! /on')
+  call VerifyScreenDump(buf, 'Test_incsearch_sort_02', {})
+  call term_sendkeys(buf, "\<Esc>")
+
   call StopVimInTerminal(buf)
   call delete('Xis_sort_script')
 endfunc

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    637,
 /**/
     636,
 /**/