i18n: mark merge CHERRY_PICK_HEAD messages for translation

Mark CHERRY_PICK_HEAD related messages in builtin/merge.c that were
added in v1.7.5-rc0~88^2~2 (Introduce CHERRY_PICK_HEAD) by Jay Soffian
for translation.

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

builtin/merge.c

@@ -1043,10 +1043,10 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	}
 	if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
 		if (advice_resolve_conflict)
-			die("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
-			    "Please, commit your changes before you can merge.");
+			die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
+			    "Please, commit your changes before you can merge."));
 		else
-			die("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).");
+			die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
 	}
 	resolve_undo_clear();