Added scripts/prefix.py for automatically prefixing version numbers

Example:
./scripts/prefix.py lfs2

Will convert the following:
lfs_* -> lfs2_*
LFS_* -> LFS2_*
-DLFS_* -> -DLFS2_*

scripts/prefix.py

@@ -0,0 +1,61 @@
+#!/usr/bin/env python
+
+# This script replaces prefixes of files, and symbols in that file.
+# Useful for creating different versions of the codebase that don't
+# conflict at compile time.
+#
+# example:
+# $ ./scripts/prefix.py lfs2
+
+import os
+import os.path
+import re
+import glob
+import itertools
+import tempfile
+import shutil
+import subprocess
+
+DEFAULT_PREFIX = "lfs"
+
+def subn(from_prefix, to_prefix, name):
+    name, count1 = re.subn('\\b'+from_prefix, to_prefix, name)
+    name, count2 = re.subn('\\b'+from_prefix.upper(), to_prefix.upper(), name)
+    name, count3 = re.subn('\\B-D'+from_prefix.upper(),
+            '-D'+to_prefix.upper(), name)
+    return name, count1+count2+count3
+
+def main(from_prefix, to_prefix=None, files=None):
+    if not to_prefix:
+        from_prefix, to_prefix = DEFAULT_PREFIX, from_prefix
+
+    if not files:
+        files = subprocess.check_output([
+                'git', 'ls-tree', '-r', '--name-only', 'HEAD']).split()
+
+    for oldname in files:
+        # Rename any matching file names
+        newname, namecount = subn(from_prefix, to_prefix, oldname)
+        if namecount:
+            subprocess.check_call(['git', 'mv', oldname, newname])
+
+        # Rename any prefixes in file
+        count = 0
+        with open(newname+'~', 'w') as tempf:
+            with open(newname) as newf:
+                for line in newf:
+                    line, n = subn(from_prefix, to_prefix, line)
+                    count += n
+                    tempf.write(line)
+        shutil.copystat(newname, newname+'~')
+        os.rename(newname+'~', newname)
+        subprocess.check_call(['git', 'add', newname])
+
+        # Summary
+        print '%s: %d replacements' % (
+                '%s -> %s' % (oldname, newname) if namecount else oldname,
+                count)
+
+if __name__ == "__main__":
+    import sys
+    sys.exit(main(*sys.argv[1:]))