[Gnu-arch-users] Re: Re: Re: [arch-users] advanced usage advice: the prism technique (fwd)

[Andrea Arcangeli]

On Sun, Sep 28, 2003 at 11:21:21AM +0200, Pau Aliagas wrote:
> On Sun, 28 Sep 2003, Paul Hedderly wrote:
> 
> > On Sat, Sep 27, 2003 at 01:40:18PM +0200, Andrea Arcangeli wrote:
> > > 
> > > > about adding an argument to `tla get' so that it would hardlink instead
> > > > of copying files from the revision library (if possible)? It escapes my
> > > 
> > > that would make it. Of course I'm playing risky, but I'm fine to deal
> > > with that risk, the payoff makes it worthwhile, it's simply up to me
> > > (not to the kernel since the kernel can't do that) to always do
> > > copy-on-write on all the checked out trees.
> > 
> > Would it be worth tla making the checked out files read-only. That way
> > if you try to edit it you get a warning at least. You would need to do a
> > "tla unlock ..." to edit it (which of course would rename and copy the
> > file, maybe restore original permissions.)
> > 
> > Just trying to think of ways to make this safer... :O)
> 
> If you change permissions in a tree, that is part of teh revision control, 
> so I don't see it feasible.

Oh good point Pau, I didn't think arch was preserving the attributes in
the patchsets. So if we mark the tree readonly the first commit would
notice all the changes in permissions that we don't want to.

Theoretically however we could teach arch to ignore any file with link
count > 1. That's quite an hack but it may work just fine. the new files
likely are created with the same permissions as the old one but only
with the writeable bit set again. However this sounds quite like a
dirty hack.

> What I see feasible is to, somehowm add an option to tla get to use 
> hardlinks to library revisions or cached revisions, instead of massive 
> copying. The library option sound easier as its exactly this.

yes, the library option sounds easier, and we should start easy by
leaving the permissions as they're supposed to be.

> I have even thought of creating library revisions as working dirs, then
> copying the {arch} dir inside. If your editor and patch copy-on-write, 
> immediate support for this special "tla get --hardlinks" would be almost 
> done :)

sounds very good ;)

Andrea - If you prefer relying on open source software, check these links:
            rsync.kernel.org::pub/scm/linux/kernel/bkcvs/linux-2.[45]/
            http://www.cobite.com/cvsps/