ls-files --error-unmatch: do not barf if the same pattern is given twice.

This is most visible when you do "git commit Makefile Makefile"; it
may be a stupid request, but that is not a reason to fail the command.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-ls-files.c

@@ -511,8 +511,28 @@ int cmd_ls_files(int argc, const char **argv, const char *prefix)
 		 */
 		int num, errors = 0;
 		for (num = 0; pathspec[num]; num++) {
+			int other, found_dup;
+
 			if (ps_matched[num])
 				continue;
+			/*
+			 * The caller might have fed identical pathspec
+			 * twice.  Do not barf on such a mistake.
+			 */
+			for (found_dup = other = 0;
+			     !found_dup && pathspec[other];
+			     other++) {
+				if (other == num || !ps_matched[other])
+					continue;
+				if (!strcmp(pathspec[other], pathspec[num]))
+					/*
+					 * Ok, we have a match already.
+					 */
+					found_dup = 1;
+			}
+			if (found_dup)
+				continue;
+
 			error("pathspec '%s' did not match any file(s) known to git.",
 			      pathspec[num] + prefix_offset);
 			errors++;