[darcs-users] BIG Mistake

[Tommy Pettersson]

On Tue, Nov 07, 2006 at 07:30:22PM +0100, Wolfgang Jeltsch wrote:
> Am Dienstag, 7. November 2006 19:04 schrieb Tommy Pettersson:
> > On Tue, Nov 07, 2006 at 10:14:41AM -0500, Jorey Bump wrote:
> > > Is it safe to  delete the corresponding (and huge) patch file, now?
> >
> > Yes. It is mainly left for debugging / crash recovery purposes,
> > but if it is a hard link and you later pull the same patch again
> > it can also be "reused" instead of being replaced with a
> > space-consuming copy.
> 
> What do you mean with “if it is a hard link”?  To my knowledge, every file on 
> a Unix-like file system has a hard link pointing to it, and creating hard 
> links explicitly just results in a file having more than one hard link 
> pointing to it.
> 
> In addition, I thought that darcs' hard link feature is just about sharing 
> patch files between repositories, not reusing previously unused patch files.
> 
> > There are plans to make Pull create hard links all by itself,
> 
> Is this about pull creating hard links to the patch files in the repository 
> pulled from?  I thought that darcs already does so.

Links are only created by Get and Optimize --relink (and maybe
Put, I don't know). All other commands that adds or modifies
patches uses a writePatch function. This function _replaces_
files, which destroys any link sharing (which is its intended
purpose). But it first checks if the file contents is already
correct, because sometimes "modified" patches haven't really
changed, so it doesn't destroy links unnecessarily. As a side
effect, a lingering patch file with the correct contents (which
happens if you Unpull and then Pull a patch) is "kept", and its
linkage is preserved.


-- 
Tommy Pettersson <ptp at lysator.liu.se>