Fix silently failing branch merge script on Mac

tools/merge-to-branch.sh

 #!/bin/bash
 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
@@ skipping 188 matching lines @@
 let CURRENT_STEP+=1
 if [ $START_STEP -le $CURRENT_STEP ] ; then
   echo ">>> Step $CURRENT_STEP: Increment version number."
   restore_if_unset "PATCH"
   NEWPATCH=$(($PATCH + 1))
   confirm "Automatically increment PATCH_LEVEL? (Saying 'n' will fire up \
 your EDITOR on $VERSION_FILE so you can make arbitrary changes. When \
 you're done, save the file and exit your EDITOR.)"
   if [ $? -eq 0 ] ; then
     sed -e "/#define PATCH_LEVEL/s/[0-9]*$/$NEWPATCH/" \
-        -i "$VERSION_FILE"
+        -i.bak "$VERSION_FILE" || die "Could not increment patch level"
   else
     $EDITOR "$VERSION_FILE"
   fi
   read_and_persist_version "NEW"
 fi
 
 let CURRENT_STEP+=1
 if [ $START_STEP -le $CURRENT_STEP ] ; then
   echo ">>> Step $CURRENT_STEP: Commit to local branch."
   git commit -a -F "$COMMITMSG_FILE" \
@@ skipping 51 matching lines @@
   restore_if_unset "TO_URL"
   restore_if_unset "REVISION_LIST"
   restore_version_if_unset "NEW"
   common_cleanup
   echo "*** SUMMARY ***"
   echo "version: $NEWMAJOR.$NEWMINOR.$NEWBUILD.$NEWPATCH"
   echo "branch: $TO_URL"
   echo "svn revision: $SVN_REVISION"
   [[ -n "$REVISION_LIST" ]] && echo "patches:$REVISION_LIST"
 fi