Create a specific version of the read_pipe_lines command for p4 invocations

This will make it easier to isolate changes to how 'p4' is invoked
 (whether with parameters or not, etc.).

Signed-off-by: Anand Kumria <wildfire@progsoc.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/fast-import/git-p4

@@ -57,6 +57,13 @@ def read_pipe_lines(c):
 
     return val
 
+def p4_read_pipe_lines(c):
+    """Specifically invoke p4 on the command supplied. """
+    real_cmd = "%s %s" % ("p4", c)
+    if verbose:
+        print real_cmd
+    return read_pipe_lines(real_cmd)
+
 def system(cmd):
     if verbose:
         sys.stderr.write("executing %s\n" % cmd)