[BUG] Changesets that create empty files produce bogus patches

[Aaron Bentley]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

I've been working on an exact-patching function for bzr.  It seems very
easy.  One problem I've found is that bogus patches are used by
note_patch.  This happens when an empty file is added to the tree:

*** added file sub/sub/emptyfile.txt //
file-id:emptyfile.txt-20050727055518-be8239eb8f9d79ca //
text-id:emptyfile.txt-20050727055518-9810517032907c49
*** added file sub/sub/nonempty.txt ...

No patch.  A patch to add an empty file might look like:
- --- /dev/null
+++ mod/sub/sub/emptyfile.txt
@@ -0,0 +1,1 @@
+
\ No newline at end of file

But we don't get anything like that in note_patch; we get an empty
string.  I think we should only feed valid patches to note_patch.

Here is a patch that will let you reproduce the problem:

- --- read_changeset.py
+++ read_changeset.py
@@ -690,6 +690,7 @@

     def note_patch(self, new_path, patch):
         """There is a patch for a given filename."""
+        assert len(patch) > 0, "invalid patch for %s" % new_path
         self.patches[new_path] = patch

     def note_deletion(self, old_path):

Aaron
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.1 (GNU/Linux)
Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org

iD8DBQFC5yd00F+nu1YWqI0RAutjAJ9/Cql6mYoxSeyPF/r1Qcy2aeT1NgCZAVlU
Rq+qRCTSuBwbUmvWTGGyjSE=
=HPQs
-----END PGP SIGNATURE-----