[darcs-devel] [issue1632] darcs changes dir/file-that-never-existed should not list any patches

[Ben Franksen]

Ben Franksen <benjamin.franksen at bessy.de> added the comment:

On Mittwoch, 30. September 2009, Eric Kow wrote:
> Eric Kow <kowey at darcs.net> added the comment:
> I haven't tried to reproduce this, but this sounds like a simple
> consequence of the filepath being filtered out and darcs changes thinking
> it's doesn't have any arguments.

Unfortunately it is not. I managed to track it down to 
Darcs.Patch.TouchesFiles.look_touch which actually gives back the wrong 
result with the test.

look_touch :: Patchy p => [FilePath] -> p C(x y) -> (Bool, [FilePath])

When I instrument this function to print out its result and run darcs 
changes d/notthere on a repo tat just contains d, (as in the test case) I 
get:

ben at sarun[1]: .../darcs/darcs.net > ./dist/build/darcs/darcs changes 
d/notthere --repodir=tests/R
Changes to d/notthere:

look_touch: (True,["./d/notthere"])
Sat Oct  3 14:31:38 CEST 2009  ben.franksen at online.de
  * added directory d

I understand that look_touch is used in many places in darcs and even if I 
managed to understand how it works (which I don't, see below) and 'fix' it, 
this would probably break other darcs commands.

Darcs.Patch.TouchesFiles.look_touch lacks any documentation. Looking at its 
code, I see that it gets the list of files by applying another undocumented 
function Darcs.Patch.Apply.apply_to_filepaths which, int turn, calls the 
undocumented method apply from class Apply. It looks as if apply doesn't 
necessarily apply a patch, depending on which instance is selected, but 
what it is /supposed/ to do if not apply the patch is beyond me to guess.

This is the point at which I gave up.

Cheers
Ben

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