i18n: git-tag tag_template message

Mark the tag_template message as translatable with N_() and then use
it later with _(). We need to skip a test under GETTEXT_POISON that
relies on the output having a leading newline.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/tag.c b/builtin/tag.c
index 4bed7c2..4242e27 100644
--- a/builtin/tag.c
+++ b/builtin/tag.c
@@ -213,10 +213,10 @@
 }
 
 static const char tag_template[] =
-	"\n"
+	N_("\n"
 	"#\n"
 	"# Write a tag message\n"
-	"#\n";
+	"#\n");
 
 static void set_signingkey(const char *value)
 {
@@ -305,7 +305,7 @@
 		if (!is_null_sha1(prev))
 			write_tag_body(fd, prev);
 		else
-			write_or_die(fd, tag_template, strlen(tag_template));
+			write_or_die(fd, _(tag_template), strlen(_(tag_template)));
 		close(fd);
 
 		if (launch_editor(path, buf, NULL)) {