Add a single command that will be used to construct the 'p4' command

Rather than having three locations where the 'p4' command is built up,
 refactor this into the one place. This will, eventually, allow us to
 have one place where we modify the evironment or pass extra
 command-line options to the 'p4' binary.

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

contrib/fast-import/git-p4

@@ -16,6 +16,17 @@ from sets import Set;
 
 verbose = False
 
+
+def p4_build_cmd(cmd):
+    """Build a suitable p4 command line.
+
+    This consolidates building and returning a p4 command line into one
+    location. It means that hooking into the environment, or other configuration
+    can be done more easily.
+    """
+    real_cmd = "%s %s" % ("p4", cmd)
+    return real_cmd
+
 def die(msg):
     if verbose:
         raise Exception(msg)