patch 9.0.0738: cannot suppress completion "scanning" messages

Problem:    Cannot suppress completion "scanning" messages.
Solution:   Add the "C" flag in 'shortmess'. (Bjorn Linse, closes #11354)

runtime/doc/options.txt

@@ -7079,6 +7079,8 @@ A jump table for the options with a short description can be found at |Q_op|.
 	  c	don't give |ins-completion-menu| messages.  For example,
 		"-- XXX completion (YYY)", "match 1 of 2", "The only match",
 		"Pattern not found", "Back at original", etc.
+	  C	don't give messages while scanning for ins-completion items,
+		for instance "scanning tags"
 	  q	use "recording" instead of "recording @a"
 	  F	don't give the file info when editing a file, like `:silent`
 		was used for the command; note that this also affects messages

src/insexpand.c

@@ -1573,7 +1573,7 @@ ins_compl_files(
     for (i = 0; i < count && !got_int && !compl_interrupted; i++)
     {
 	fp = mch_fopen((char *)files[i], "r");  // open dictionary file
-	if (flags != DICT_EXACT)
+	if (flags != DICT_EXACT && !shortmess(SHM_COMPLETIONSCAN))
 	{
 	    msg_hist_off = TRUE;	// reset in msg_trunc_attr()
 	    vim_snprintf((char *)IObuff, IOSIZE,
@@ -3281,6 +3281,8 @@ process_next_cpt_value(
 	    st->dict = st->ins_buf->b_fname;
 	    st->dict_f = DICT_EXACT;
 	}
+	if (!shortmess(SHM_COMPLETIONSCAN))
+	{
 	    msg_hist_off = TRUE;	// reset in msg_trunc_attr()
 	    vim_snprintf((char *)IObuff, IOSIZE, _("Scanning: %s"),
 		    st->ins_buf->b_fname == NULL
@@ -3290,6 +3292,7 @@ process_next_cpt_value(
 			    : st->ins_buf->b_sfname);
 	    (void)msg_trunc_attr((char *)IObuff, TRUE, HL_ATTR(HLF_R));
 	}
+    }
     else if (*st->e_cpt == NUL)
 	status = INS_COMPL_CPT_END;
     else
@@ -3316,11 +3319,14 @@ process_next_cpt_value(
 #endif
 	else if (*st->e_cpt == ']' || *st->e_cpt == 't')
 	{
-	    msg_hist_off = TRUE;	// reset in msg_trunc_attr()
 	    compl_type = CTRL_X_TAGS;
+	    if (!shortmess(SHM_COMPLETIONSCAN))
+	    {
+		msg_hist_off = TRUE;	// reset in msg_trunc_attr()
 		vim_snprintf((char *)IObuff, IOSIZE, _("Scanning tags."));
 		(void)msg_trunc_attr((char *)IObuff, TRUE, HL_ATTR(HLF_R));
 	    }
+	}
 	else
 	    compl_type = -1;
 

src/option.h

@@ -265,11 +265,12 @@ typedef enum {
 #define SHM_ATTENTION	'A'		// no ATTENTION messages
 #define SHM_INTRO	'I'		// intro messages
 #define SHM_COMPLETIONMENU  'c'		// completion menu messages
+#define SHM_COMPLETIONSCAN  'C'		// completion scanning messages
 #define SHM_RECORDING	'q'		// short recording message
 #define SHM_FILEINFO	'F'		// no file info messages
 #define SHM_SEARCHCOUNT  'S'		// search stats: '[1/10]'
 #define SHM_POSIX       "AS"		// POSIX value
-#define SHM_ALL		"rmfixlnwaWtToOsAIcqFS" // all possible flags for 'shm'
+#define SHM_ALL		"rmfixlnwaWtToOsAIcCqFS" // all possible flags for 'shm'
 
 // characters for p_go:
 #define GO_TERMINAL	'!'		// use terminal for system commands

src/version.c

@@ -699,6 +699,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    738,
 /**/
     737,
 /**/