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Re: [Gnu-arch-users] Re: give us a hand with arch

From: Andrea Arcangeli
Subject: Re: [Gnu-arch-users] Re: give us a hand with arch
Date: Sun, 28 Sep 2003 12:58:25 +0200
User-agent: Mutt/1.4.1i

On Sun, Sep 28, 2003 at 07:57:10PM +1000, Robert Collins wrote:
> On Sun, 2003-09-28 at 19:38, Andrea Arcangeli wrote:
> > I already made the point that to be universal and to work with all sorts
> > of languages and binary formats, you *can't* mix data with metadata. The
> > default mode should be changed to be explicit, then if you want to leave
> > tagline for backwards compatibility or for smaller projects that's
> > certainly fine with me.
> Bah, I started to answer your email point by point.
> Lets just say:
> taglines are an advance over explicit, not suitable for all projects,
> but shortly, when per dir regexs exist, they will be suitable for all
> projects. They handle binary and textual data *just fine* (especially
> when combined with some explicit tagging). There is little interest
> *here* that I've observed in removing the tagline concept. I'm a
> hardened explicit mode user BTW, so this isn't 'biased cause I like it'
> talk.
> May I suggest:
> * If you don't want to use taglines thats fine: they are optional.

sure ;), that's fine with me, I don't really want to force anything to
anybody. I'm just trying to explain why I think explicit is better.

> * If you trust the folk here who have been using arch for more than a
> few days ;) then please set your tagging-method to tagline (even though
> you plan to use explicit everywhere). We aren't *ignorant*. 

I'm not saying you're ignorant. I do see the value of taglines, but I
believe you simply have been forced to mix data with metadata, and to
expose the metadata to the eyes of the user, just because you lack
features from the posix API, you want a second channel in the inode
where you can store this metadata.

You must admit that if you had this second channel the explicit would
obsolete the taglines *completely* and it would be completely wasteful
to leave the taglines metadata inlined and mixed with the data.

This is the proof the tagline is just a workaround for the lack of a
feature you want from the filesystem.

If you had this second channel in the filesystem where to store the
metadata created dynamically by arch to manage the changesets, then
explicit would match tagline, period. the data wouldn't need to be
parsed at all, it wouldn't need to be included in the tar.gz packages,
you would fetch the metadata from the second channel and you would
recreated it dynamically and *safely* every time you do a new import
into arch.

> * Your arguments about pollution are quite specious, and not backed up
> by any empirical evidence I'm aware of. You might want to review your
> assumptions before you discard the concepts out of hand. Given that
> users can grab source via arch, it's not resonable to handwave that

the majority of the users in some big project may not fetch the source
via arch.

> users 'find it worthless' when, if the tools are easy, they may well
> find it *invaluable*.
> * Whilst I'm positive that arch will be improved to meet kernel hackers
> needs, dropping or even deprecating tagline would not be an improvement.
> I think you need to really *test* tagline behaviour and facilities - for
> example exports *through* another RCS system without data loss - before
> dismissing them out of hand. 

I don't understand very well the export through another RCS point sorry,
could you elaborate?

> Really it's quite disappointing the depth of your (apparent) prejuidice.

No need to be disappointed, the tagline is the best you can do w/o
kernel support to make it trasparent as it should have been (assuming
you don't want to call move-tag and friends). It's just that I prefer
having to call move-tag/add-tag/delete-tag then to pollute the data with
metadata in non standard formats and that doesn't provide math safety
across the tree since anybody can add "arch-tag: foo" simultaneously in
all files. The day we'll have multiple channels in the inode, or a way
to bind two files together, we won't need to call move-tag and friends
anymore, and still it will be the explicit mode, never the tagline.

Andrea - If you prefer relying on open source software, check these links:

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