git-p4: disable-rebase: allow setting this via configuration

This just lets you set the --disable-rebase option with the
git configuration options git-p4.disableRebase. If you're
using this option, you probably want to set it all the time
for a given repo.

Signed-off-by: Luke Diamand <luke@diamand.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-p4.txt

@@ -342,7 +342,7 @@ These options can be used to modify 'git p4 submit' behavior.
 
 --disable-rebase::
     Disable the automatic rebase after all commits have been successfully
-    submitted.
+    submitted. Can also be set with git-p4.disableRebase.
 
 Rebase options
 ~~~~~~~~~~~~~~
@@ -658,6 +658,9 @@ git-p4.conflict::
 	Specify submit behavior when a conflict with p4 is found, as per
 	--conflict.  The default behavior is 'ask'.
 
+git-p4.disableRebase::
+    Do not rebase the tree against p4/master following a submit.
+
 IMPLEMENTATION DETAILS
 ----------------------
 * Changesets from p4 are imported using Git fast-import.

git-p4.py

@@ -1368,7 +1368,7 @@ class P4Submit(Command, P4UserMap):
         self.shelve = False
         self.update_shelve = list()
         self.commit = ""
-        self.disable_rebase = False
+        self.disable_rebase = gitConfigBool("git-p4.disableRebase")
         self.prepare_p4_only = False
         self.conflict_behavior = None
         self.isWindows = (platform.system() == "Windows")