setup: split "extensions found" messages into singular and plural

It's easier to translate this way.

Signed-off-by: Alex Henrie <alexhenrie24@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

setup.c

diff --git a/setup.c b/setup.c
index 59e2fac..ead2f80 100644
--- a/setup.c
+++ b/setup.c
@@ -666,7 +666,9 @@ int verify_repository_format(const struct repository_format *format,
 	if (format->version >= 1 && format->unknown_extensions.nr) {
 		int i;
 
-		strbuf_addstr(err, _("unknown repository extensions found:"));
+		strbuf_addstr(err, Q_("unknown repository extension found:",
+				      "unknown repository extensions found:",
+				      format->unknown_extensions.nr));
 
 		for (i = 0; i < format->unknown_extensions.nr; i++)
 			strbuf_addf(err, "\n\t%s",
@@ -678,7 +680,9 @@ int verify_repository_format(const struct repository_format *format,
 		int i;
 
 		strbuf_addstr(err,
-			      _("repo version is 0, but v1-only extensions found:"));
+			      Q_("repo version is 0, but v1-only extension found:",
+				 "repo version is 0, but v1-only extensions found:",
+				 format->v1_only_extensions.nr));
 
 		for (i = 0; i < format->v1_only_extensions.nr; i++)
 			strbuf_addf(err, "\n\t%s",