advice: move advice.graftFileDeprecated squashing to commit.[ch]

Move the squashing of the advice.graftFileDeprecated advice over to an
external variable in commit.[ch], allowing advice() to purely use the
new-style API of invoking advice() with an enum.

See 8821e90a09 (advice: don't pointlessly suggest
--convert-graft-file, 2018-11-27) for why quieting this advice was
needed. It's more straightforward to move this code to commit.[ch] and
use it builtin/replace.c, than to go through the indirection of
advice.[ch].

Because this was the last advice_config variable we can remove that
old facility from advice.c.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

advice.c

@@ -4,8 +4,6 @@
 #include "help.h"
 #include "string-list.h"
 
-int advice_graft_file_deprecated = 1;
-
 static int advice_use_color = -1;
 static char advice_colors[][COLOR_MAXLEN] = {
 	GIT_COLOR_RESET,
@@ -33,13 +31,6 @@ static const char *advise_get_color(enum color_advice ix)
 	return "";
 }
 
-static struct {
-	const char *name;
-	int *preference;
-} advice_config[] = {
-	{ "graftFileDeprecated", &advice_graft_file_deprecated },
-};
-
 static struct {
 	const char *key;
 	int enabled;
@@ -162,13 +153,6 @@ int git_default_advice_config(const char *var, const char *value)
 	if (!skip_prefix(var, "advice.", &k))
 		return 0;
 
-	for (i = 0; i < ARRAY_SIZE(advice_config); i++) {
-		if (strcasecmp(k, advice_config[i].name))
-			continue;
-		*advice_config[i].preference = git_config_bool(var, value);
-		break;
-	}
-
 	for (i = 0; i < ARRAY_SIZE(advice_setting); i++) {
 		if (strcasecmp(k, advice_setting[i].key))
 			continue;