Re: Re: Merge with git-pasky II.

Dear diary, on Thu, Apr 14, 2005 at 09:59:04PM CEST, I got a letter
where Junio C Hamano [off-list ref] told me that...

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"LT" == Linus Torvalds [off-list ref] writes:

LT> On Thu, 14 Apr 2005, Junio C Hamano wrote:

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Sorry, I have not seen what you have been doing since pasky 0.3,
and I have not even started to understand the mental model of
the world your tool is building.  That said, my gut feeling is
that telling this script about git-pasky's world model might be
a mistake.  I'd rather see you consider the script as mere "part
of the plumbing". 

LT> I agree. Having separate abstraction layers is good.  I'm actually very 
LT> happy with Pasky's cleaned-up-tree, exactly because unlike the first one, 

(Just a side-note - functionally and even organizationally, the cleaned
up tree does not differ significantly from the original one.)

LT> Pasky did a great job of maintaining the abstraction between "plumbing" 
LT> and user interfaces.

Agreed, not just with your agreeing with me, but with the
statement that Pasky did a good job (although I am ashamed to
say I have not caught up with the "userland" tools).

Thanks. :-)

LT> The plumbing should take user interface needs into account, but the more
LT> conceptually separate it is ("does it makes sense on its own?") the better
LT> off we'll be. And "merge these two trees" (which works on a _tree_ level)
LT> or "find the common commit" (which works on a _commit_ level) look like 
LT> plumbing to me - the kind of things I should have written, if I weren't 
LT> such a lazy slob.

I am planning drop the ancestor computation from the script, and
make it another command line parameter to the script.  Dan
Barkalow's merge-base program should be used to compute it and
his result should drive the merge.  That sounds more UNIXy to
me.

Good move, I say!

I even may want to make the script take three trees not
commits, since the merge script does not need commits (it only
needs trees).  As plumbing it would be cleaner interface to it
to do so.  The wrapper SCM scripts can and should make sure it
is fed trees when the user gives it commits (or symbolic
representation of it like .git/tags/blah, or `cat .git/HEAD`).

Agreed.

But one different thing to note here.

You say "merge these two trees" above (I take it that you mean
"merge these two trees, taking account of this tree as their
common ancestor", so actually you are dealing with three trees),
and I am tending to agree with the notion of merging trees not
commits.  However you might get richer context and more sensible
resulting merge if you say "merge these two commits".  Since
commit chaining is part of the fundamental git object model you
may as well use it.

Could you be more particular on the richer context etc?

I think this script should stay strictly on the level of trees. When
someone invents it, there could be a merge-commits script which does
something very smart about two commits, traversing the graph between
them etc, and doing a set of merge-tree invocations, possibly preparing
the staging area for them etc.

-- 
				Petr "Pasky" Baudis
Stuff: http://pasky.or.cz/
C++: an octopus made by nailing extra legs onto a dog. -- Steve Taylor