Re: [Monotone-devel] Re: mtnpatch (updated)

[Nathaniel Smith]

On Sun, Mar 11, 2007 at 03:59:12PM +0100, cyril Romain wrote:
> Maybe I've just missed the right mtn command reading the documentation, 
> but as I'm submitting some patches/recipes for OE metadata, I'd like to:
> 1. test that my 'mtn diff' patches successfully apply on a up-to-date 
> metadata tree without any local modifications.
> 2. apply some patches to another development tree.
> 
> And this script is "almost" what I'm looking for :)

Not sure I understand what exactly you're trying to do here, and would
be curious if 'mtn pluck' would work for you, or if not, why not...

> "Almost" because it does not takes file/directory drop order into 
> account, i.e. "mtnpatch.py the.patch | sh" can fail.
> For example if mtnpatch dumps:
> ---
> mtn drop -e packages/quilt/files/install.patch
> mtn drop -e packages/quilt/files
> ---
> And if you run these commands in that order, you get "mtn: misuse: 
> cannot remove packages/quilt/files/, it is not empty"
> 
> In attachment, an updated version of mtnpatch.py with the following 
> improvements:
> 1. output command are sorted, so that 'mtnpatch.py my_patch.patch | sh' 
> should now succeed in all cases, hopefully :)

It won't.  To handle arbitrary add/drop/renames, you have to do
somewhat complicated things.  The simplest example is:
   rename a b
   rename b a
(i.e., interchange the two files.)  Obviously there's no order you can
put those in that will work, you need to move one out of the way to a
temporary location first...

Other complicated cases involve intermixing different file operations,
like
  add b
  rename a/foo b/foo
  drop a
  add b/foo/baz
Here you have to do things in this order in particular, or it won't
work.

This is all solvable with the right sort of abstraction, I think there
are some comments about it in cset.cc, but it requires a trick.  The
best _documentation_ of the trick is probably this blog post that
Aaron Bentley wrote:
  
http://mebentley.blogspot.com/2005/12/tree-transforms-on-posix-filesystems.html

I don't know that you care, though :-).

-- Nathaniel

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