contrib: fix special character handling in filter-lamely

filter-lamely does not handle filenames with special characters (such as
äöü or even \n and \t) properly when using a tree filter or index
filter. It either does not quote the input to git correctly or parses
git output incorrectly, causing affected filenames to be mangled with
extraneous double quotes in the history or even crashing the program.

Make filter-lamely correctly handle such filenames by using
NUL-delimited input and output modes for the affected git commands.

Signed-off-by: Marius Renner <marius@mariusrenner.de>

contrib/filter-repo-demos/filter-lamely

@@ -385,7 +385,7 @@ class UserInterfaceNightmare:
     # manually sets GIT_ALLOW_NULL_SHA1, so to pass the same tests we need to
     # as well.
     os.environ['GIT_ALLOW_NULL_SHA1'] = '1'
-    p = subproc.Popen('git update-index --index-info'.split(),
+    p = subproc.Popen('git update-index -z --index-info'.split(),
                       stdin = subprocess.PIPE)
     for change in file_changes:
       if change.type == b'D':
@@ -393,10 +393,10 @@ class UserInterfaceNightmare:
         # case they are renaming all files (e.g. moving into a subdirectory);
         # they need to be able to rename what is deleted so it actually deletes
         # the right thing.
-        p.stdin.write(b'160000 %s\t%s\n'
+        p.stdin.write(b'160000 %s\t%s\x00'
                       % (self._special_delete_mode, change.filename))
       else:
-        p.stdin.write(b'%s %s\t%s\n' %
+        p.stdin.write(b'%s %s\t%s\x00' %
                       (change.mode, change.blob_id, change.filename))
     p.stdin.close()
     if p.wait() != 0:
@@ -405,8 +405,10 @@ class UserInterfaceNightmare:
 
   def _update_file_changes_from_index(self, commit):
     new_changes = {}
-    output = subproc.check_output('git ls-files -s'.split())
-    for line in output.splitlines():
+    output = subproc.check_output('git ls-files -sz'.split())
+    for line in output.split(b'\x00'):
+      if not line:
+        continue
       mode_thru_stage, filename = line.split(b'\t', 1)
       mode, objid, stage = mode_thru_stage.split(b' ')
       if mode == b'160000' and objid == self._special_delete_mode: