move struct pathspec and related functions to pathspec.[ch]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/ls-tree.c b/builtin/ls-tree.c
index fb76e38..93fc3a0 100644
--- a/builtin/ls-tree.c
+++ b/builtin/ls-tree.c
@@ -10,6 +10,7 @@
 #include "quote.h"
 #include "builtin.h"
 #include "parse-options.h"
+#include "pathspec.h"
 
 static int line_termination = '\n';
 #define LS_RECURSIVE 1