bug#3224: 23.0.92; vc-dir vs uniquify: wrong directory used

[Dan Nicolaescu <dann@ics.uci.edu>]

Juanma Barranquero <lekktu@gmail.com> writes:

  > On Wed, Jan 6, 2010 at 15:28, Stefan Monnier <monnier@iro.umontreal.ca> wrote:
  > 
  > > AFAIK it already *does* the right thing (try it with Dired buffers,
  > > since these are the (only?) ones that should have a directory name),
  > > unless maybe we don't agree on what is the right thing in that case.
  > 
  > The dired and vc-dired cases are not exactly equivalent. In the dired
  > case, uniquify-buffer-file-name is called when there's a conflict like
  > 
  >   (dired "/my/dir-1/A")
  >   (dired "/my/dir-2/A")
  > 
  > (because /my/dir/A vs my/dir/B obviously does not produce any conflict).
  > 
  > In this case, u-b-f-n gets, via `list-buffers-directory', the full
  > path including the A:  /my/dir1/A, and strips the last element and
  > returns /my/dir1. That works for uniquify, because it will be getting
  > path elements from /my/dir1 vs. /my/dir2, just as it needs. The
  > resulting buffers (with forward syntax) will be "A|dir-1" and
  > "A|dir-2".
  > 
  > In the OP's vc-dir case, the conflicts happens in this:
  > 
  >   (vc-dir "/my/dir/A")
  >   (vc-dir "/my/dir/B")
  > 
  > because the conflict uniquify tries to solve is at the buffer-name
  > level, which is always *vc-dir*. /my/dir/A and /my/dir/B are
  > directories, and so elements for uniquifying; the expected result is
  > "*vc-dir*|A" and "*vc-dir*|B". However, u-b-f-n gets "/my/dir/B" (via
  > list-buffers-directory), which is correct, and again strips the last
  > element and returns "/my/dir". So uniquify ends producting
  > "*vc-dir*|A" and "*vc-dir*|dir", which is incorrect.
  > 
  > Now, if you consider than always removing an element from BUFFER is
  > the right thing to do for u-b-f-n, we'll have to agree to disagree;
  > IMHO, that's not what its docstring says. From it, I would expect
  > u-b-f-n to return a directory unchanged. That said, my "fix" to
  > u-b-f-n would break uniquifying of dired buffers (thanks for pointing
  > that out), so perhaps we'll have to live with such behavior. In that
  > case, I'd suggest reworking the docstring of u-b-f-n.
  > 
  > Going with your proposed fix via `list-buffers-directory', the
  > following patch works. I have not added a comment to the change to
  > `list-buffers-directory' because I don't really know how to explain
  > it; it seems a hack to me to force a variable named
  > `list-buffers-directory' to contain a bogus name part just to help
  > uniquify.
  > 
  > Comments? Dan, what do you think?

Does it work if you have multiple *vc-dir* buffers for the same
directory?
Do something like:
mkdir /tmp/test
cd /tmp/test
git init
bzr init

C-u C-x v d /tmp/test RET Bzr RET
C-u C-x v d /tmp/test RET Git RET

I'm fine with it if you convince Stefan this is TRTD.