git-p4.py: support Python 2.4

Python 2.4 lacks the following features:

   subprocess.check_call
   struct.pack_into

Take a cue from 460d102 and provide an implementation of the
CalledProcessError exception.  Then replace the calls to
subproccess.check_call with calls to subprocess.call that check the return
status and raise a CalledProcessError exception if necessary.

The struct.pack_into in t/9802 can be converted into a single struct.pack
call which is available in Python 2.4.

Signed-off-by: Brandon Casey <bcasey@nvidia.com>
Acked-by: Pete Wyckoff <pw@padd.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

INSTALL

@@ -131,7 +131,7 @@ Issues of note:
 	  use English. Under autoconf the configure script will do this
 	  automatically if it can't find libintl on the system.
 
-	- Python version 2.5 or later is needed to use the git-p4
+	- Python version 2.4 or later is needed to use the git-p4
 	  interface to Perforce.
 
  - Some platform specific issues are dealt with Makefile rules,

git-p4.py

@@ -12,6 +12,21 @@
 import tempfile, getopt, os.path, time, platform
 import re, shutil
 
+try:
+    from subprocess import CalledProcessError
+except ImportError:
+    # from python2.7:subprocess.py
+    # Exception classes used by this module.
+    class CalledProcessError(Exception):
+        """This exception is raised when a process run by check_call() returns
+        a non-zero exit status.  The exit status will be stored in the
+        returncode attribute."""
+        def __init__(self, returncode, cmd):
+            self.returncode = returncode
+            self.cmd = cmd
+        def __str__(self):
+            return "Command '%s' returned non-zero exit status %d" % (self.cmd, self.returncode)
+
 verbose = False
 
 # Only labels/tags matching this will be imported/exported
@@ -152,13 +167,17 @@ def system(cmd):
     expand = isinstance(cmd,basestring)
     if verbose:
         sys.stderr.write("executing %s\n" % str(cmd))
-    subprocess.check_call(cmd, shell=expand)
+    retcode = subprocess.call(cmd, shell=expand)
+    if retcode:
+        raise CalledProcessError(retcode, cmd)
 
 def p4_system(cmd):
     """Specifically invoke p4 as the system command. """
     real_cmd = p4_build_cmd(cmd)
     expand = isinstance(real_cmd, basestring)
-    subprocess.check_call(real_cmd, shell=expand)
+    retcode = subprocess.call(real_cmd, shell=expand)
+    if retcode:
+        raise CalledProcessError(retcode, real_cmd)
 
 def p4_integrate(src, dest):
     p4_system(["integrate", "-Dt", wildcard_encode(src), wildcard_encode(dest)])
@@ -3104,7 +3123,9 @@ def run(self, args):
         init_cmd = [ "git", "init" ]
         if self.cloneBare:
             init_cmd.append("--bare")
-        subprocess.check_call(init_cmd)
+        retcode = subprocess.call(init_cmd)
+        if retcode:
+            raise CalledProcessError(retcode, init_cmd)
 
         if not P4Sync.run(self, depotPaths):
             return False

t/t9802-git-p4-filetype.sh

@@ -105,12 +105,13 @@ build_gendouble() {
 	cat >gendouble.py <<-\EOF
 	import sys
 	import struct
-	import array
 
-	s = array.array("c", '\0' * 26)
-	struct.pack_into(">L", s,  0, 0x00051607)  # AppleDouble
-	struct.pack_into(">L", s,  4, 0x00020000)  # version 2
-	s.tofile(sys.stdout)
+	s = struct.pack(">LL18s",
+			0x00051607,  # AppleDouble
+			0x00020000,  # version 2
+			""           # pad to 26 bytes
+	)
+	sys.stdout.write(s)
 	EOF
 }