Re: Re: GIT license (Re: Re: Re: Re: Re: [ANNOUNCE] git-pasky-0.1)

Re: Re: GIT license (Re: Re: Re: Re: Re: [ANNOUNCE] git-pasky-0.1)

[Adam J. Richter]

On Mon, 11 Apr 2005 20:45:38 +0200, Peter Baudis wrote:
>  Hello,

>  please do not trim the cc list so agressively.

Sorry.  I read the list from a web site that does not show the
cc lists.  I'll try to cc more people from the relevant discussions
though.  On the other hand, I've dropped Linus from this message,
as it just points to something he previously said.

>Dear diary, on Mon, Apr 11, 2005 at 05:46:38PM CEST, I got a letter
>where "Adam J. Richter" <adam@yggdrasil.com> told me that...
>..snip..
>> Graydon Hoare.  (By the way, I would prefer that git just punt to
>> user level programs for diff and merge when all of the versions
>> involved are different or at least have a very thin interface
>> for extending the facility, because I would like to do some character
>> based merge stuff.)
>..snip..

>But this is what git already does. I agree it could do it even better,
>by checking environment variables for the appropriate tools (then you
>could use that to pass diff e.g. -p etc.).

This message from Linus seemed to imply that git was going to get
its own 3-way merge code:

| Then the bad news: the merge algorithm is going to suck. It's going to be
| just plain 3-way merge, the same RCS/CVS thing you've seen before. With no
| understanding of renames etc. I'll try to find the best parent to base the
| merge off of, although early testers may have to tell the piece of crud
| what the most recent common parent was.

( from http://marc.theaimsgroup.com/?l=linux-kernel&m=111320013100822&w=2 )


                    __     ______________
Adam J. Richter        \ /
adam@yggdrasil.com      | g g d r a s i l

Re: Re: Re: GIT license (Re: Re: Re: Re: Re: [ANNOUNCE] git-pasky-0.1)

[Petr Baudis]

Dear diary, on Tue, Apr 12, 2005 at 03:20:18AM CEST, I got a letter
where "Adam J. Richter" <adam@yggdrasil.com> told me that...
> >Dear diary, on Mon, Apr 11, 2005 at 05:46:38PM CEST, I got a letter
> >where "Adam J. Richter" <adam@yggdrasil.com> told me that...
> >..snip..
> >> Graydon Hoare.  (By the way, I would prefer that git just punt to
> >> user level programs for diff and merge when all of the versions
> >> involved are different or at least have a very thin interface
> >> for extending the facility, because I would like to do some character
> >> based merge stuff.)
> >..snip..
> 
> >But this is what git already does. I agree it could do it even better,
> >by checking environment variables for the appropriate tools (then you
> >could use that to pass diff e.g. -p etc.).
> 
> This message from Linus seemed to imply that git was going to get
> its own 3-way merge code:
> 
> | Then the bad news: the merge algorithm is going to suck. It's going to be
> | just plain 3-way merge, the same RCS/CVS thing you've seen before. With no
> | understanding of renames etc. I'll try to find the best parent to base the
> | merge off of, although early testers may have to tell the piece of crud
> | what the most recent common parent was.

Well, from what I can read it says "just plain 3-way merge, the same
RCS/CVS thing you've seen before". :-)

Basically, when you look at merge(1) :

SYNOPSIS
       merge [ options ] file1 file2 file3
DESCRIPTION
       merge  incorporates  all  changes that lead from file2 to file3
into file1.

The only big problem is how to guess the best file2 when you give it
file3 and file1.

-- 
				Petr "Pasky" Baudis
Stuff: http://pasky.or.cz/
98% of the time I am right. Why worry about the other 3%.

Re: Re: Re: GIT license (Re: Re: Re: Re: Re: [ANNOUNCE] git-pasky-0.1)

[Geert Uytterhoeven]

On Tue, 12 Apr 2005, Petr Baudis wrote:
> Dear diary, on Tue, Apr 12, 2005 at 03:20:18AM CEST, I got a letter
> where "Adam J. Richter" <adam@yggdrasil.com> told me that...
> > >Dear diary, on Mon, Apr 11, 2005 at 05:46:38PM CEST, I got a letter
> > >where "Adam J. Richter" <adam@yggdrasil.com> told me that...
> > >..snip..
> > >> Graydon Hoare.  (By the way, I would prefer that git just punt to
> > >> user level programs for diff and merge when all of the versions
> > >> involved are different or at least have a very thin interface
> > >> for extending the facility, because I would like to do some character
> > >> based merge stuff.)
> > >..snip..
> > 
> > >But this is what git already does. I agree it could do it even better,
> > >by checking environment variables for the appropriate tools (then you
> > >could use that to pass diff e.g. -p etc.).
> > 
> > This message from Linus seemed to imply that git was going to get
> > its own 3-way merge code:
> > 
> > | Then the bad news: the merge algorithm is going to suck. It's going to be
> > | just plain 3-way merge, the same RCS/CVS thing you've seen before. With no
> > | understanding of renames etc. I'll try to find the best parent to base the
> > | merge off of, although early testers may have to tell the piece of crud
> > | what the most recent common parent was.
> 
> Well, from what I can read it says "just plain 3-way merge, the same
> RCS/CVS thing you've seen before". :-)
> 
> Basically, when you look at merge(1) :
> 
> SYNOPSIS
>        merge [ options ] file1 file2 file3
> DESCRIPTION
>        merge  incorporates  all  changes that lead from file2 to file3
> into file1.
> 
> The only big problem is how to guess the best file2 when you give it
> file3 and file1.

That's either the point just before you started modifying the file, or your
last merge point. Sounds simple, but if your SCM system doesn't track merges,
your SOL...

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

Re: Re: Re: Re: GIT license (Re: Re: Re: Re: Re: [ANNOUNCE] git-pasky-0.1)

[Petr Baudis]

Dear diary, on Tue, Apr 12, 2005 at 10:39:40AM CEST, I got a letter
where Geert Uytterhoeven <geert@linux-m68k.org> told me that...
> On Tue, 12 Apr 2005, Petr Baudis wrote:
..snip..
> > Basically, when you look at merge(1) :
> > 
> > SYNOPSIS
> >        merge [ options ] file1 file2 file3
> > DESCRIPTION
> >        merge  incorporates  all  changes that lead from file2 to file3
> > into file1.
> > 
> > The only big problem is how to guess the best file2 when you give it
> > file3 and file1.
> 
> That's either the point just before you started modifying the file, or your
> last merge point. Sounds simple, but if your SCM system doesn't track merges,
> your SOL...

Well, yes, but the last merge point search may not be so simple:

A --1---2----6---7
B    \   `-4-.  /
C     `-3-----5'

Now, when at 7, your last merge point is not 1, but 2.

What I have proposed at the git mailing list was to have simple merging
tracking - merges/branch1/branch2 directory structure which would store
merges from branch2 to branch1. Then, when merging say to branch3, you
traverse all of them and if any of the branch1/* commits is newer than
branch3/*, you update it.

The disadvantage is that you now need to strictly use gitmerge.sh to do
the merges - Linus' revtree solution is nicer in the regard that it
works without any explicit bookkeeping, and tracks any merges properly
recorded with commit-file; it is more complex and more expensive,
though.

-- 
				Petr "Pasky" Baudis
Stuff: http://pasky.or.cz/
98% of the time I am right. Why worry about the other 3%.

Re: Re: Re: Re: Re: GIT license (Re: Re: Re: Re: Re: [ANNOUNCE] git-pasky-0.1)

[Petr Baudis]

Dear diary, on Tue, Apr 12, 2005 at 11:50:48AM CEST, I got a letter
where Petr Baudis <pasky@ucw.cz> told me that...
> Dear diary, on Tue, Apr 12, 2005 at 10:39:40AM CEST, I got a letter
> where Geert Uytterhoeven <geert@linux-m68k.org> told me that...
> > On Tue, 12 Apr 2005, Petr Baudis wrote:
> ..snip..
> > > Basically, when you look at merge(1) :
> > > 
> > > SYNOPSIS
> > >        merge [ options ] file1 file2 file3
> > > DESCRIPTION
> > >        merge  incorporates  all  changes that lead from file2 to file3
> > > into file1.
> > > 
> > > The only big problem is how to guess the best file2 when you give it
> > > file3 and file1.
> > 
> > That's either the point just before you started modifying the file, or your
> > last merge point. Sounds simple, but if your SCM system doesn't track merges,
> > your SOL...
> 
> Well, yes, but the last merge point search may not be so simple:
> 
> A --1---2----6---7
> B    \   `-4-.  /
> C     `-3-----5'
> 
> Now, when at 7, your last merge point is not 1, but 2.

...and this is obviously wrong, sorry. You would lose 3 this way.

-- 
				Petr "Pasky" Baudis
Stuff: http://pasky.or.cz/
98% of the time I am right. Why worry about the other 3%.

Re: GIT license (Re: Re: Re: Re: Re: [ANNOUNCE] git-pasky-0.1)

[Chris Friesen]

Petr Baudis wrote:
> Dear diary, on Tue, Apr 12, 2005 at 11:50:48AM CEST, I got a letter

>>Well, yes, but the last merge point search may not be so simple:
>>
>>A --1---2----6---7
>>B    \   `-4-.  /
>>C     `-3-----5'
>>
>>Now, when at 7, your last merge point is not 1, but 2.
> 
> 
> ...and this is obviously wrong, sorry. You would lose 3 this way.

Wouldn't the delta betweeen 2 and 5 include any contribution from 3?

Chris

Re: GIT license (Re: Re: Re: Re: Re: [ANNOUNCE] git-pasky-0.1)

[Adam J. Richter]

On 2005-04-11, Linus Torvalds wrote:
>I'm inclined to go with GPLv2 just because it's the most common one [...]

	You may want to use a file from GPL'ed monotone that
implements a substantial diff optimization described in the August
1989 paper by Sun Wu, Udi Manber and Gene Myers ("An O(NP) Sequence
Comparison Algorithm").  According to th file, that implementation
was a port of some Scheme code written by Aubrey Jaffer to C++ by
Graydon Hoare.  (By the way, I would prefer that git just punt to
user level programs for diff and merge when all of the versions
involved are different or at least have a very thin interface
for extending the facility, because I would like to do some character
based merge stuff.)

	It looks to me like the anti-patent provisions of OSLv2.1
could be circumvented by an offender creating a separate company
to do patent litigation.  So, I think you'll find that the software
reuse benefits (both to GIT and to other software projects) of the
more widely used GPL ougtweigh the anti-patent benefits of OSLv2.1.

	Although I like the idea of anti-patent provisions, such
as those in OSLv2.1, I think mutual compatability of free
software is probably more consequential, even from a purely
political perspective.

	Perhaps you might want to consider offering the code
under the distributor's choice of either license if you want
to offer the very minor benefits of slightly easier compliance
to those who do not litigate software patents, or, perhaps more
importantly, the ability of the software to be copied into
OSLv2.1 projects (if there are any).

                    __     ______________ 
Adam J. Richter        \ /
adam@yggdrasil.com      | g g d r a s i l

Re: GIT license (Re: Re: Re: Re: Re: [ANNOUNCE] git-pasky-0.1)

[Nur Hussein]

> Btw, does anybody have strong opinions on the license? I didn't put in a 
> COPYING file exactly because I was torn between GPLv2 and OSL2.1.

I think GPLv2 would create the least amount of objection in the
community, so I'd probably want to go with that.

		Nur Hussein

[ANNOUNCE] git-pasky-0.1

[Petr Baudis]

  Hello,

  so I "released" git-pasky-0.1, my set of patches and scripts upon
Linus' git, aimed at human usability and to an extent a SCM-like usage.

  You can get it at

	http://pasky.or.cz/~pasky/dev/git/git-pasky-base.tar.bz2

and after unpacking and building (make) do

	git pull pasky

to get the latest changes from my branch. If you already have some git
from my branch which can do pulling, you can bring yourself up to date
by doing just

	gitpull.sh pasky

(but this style of usage is deprecated now). Please see the README for
some details regarding usage etc. You can find the changes from the last
announcement in the ChangeLog (the previous announcement corresponds to
commit id 5125d089ad862f16a306b4942155092e1dce1c2d). The most important
change is probably recursive diff addition, and making git ignore the
nsec of ctime and mtime, since it is totally unreliable and likes to
taint random files as modified.

  My near future plans include especially some merge support; I think it
should be rather easy, actually. I'll also add some simple tagging
mechanism. I've decided to postpone the file moving detection, since
there's no big demand for it now. ;-)

  I will also need to do more testing on the linux kernel tree.
Committing patch-2.6.7 on 2.6.6 kernel and then diffing results in

	$ time gitdiff.sh `parent-id` `tree-id` >p
	real    5m37.434s
	user    1m27.113s
	sys     2m41.036s

which is pretty horrible, it seems to me. Any benchmarking help is of
course welcomed, as well as any other feedback.

  BTW, what would be the best (most complete) source for the BK tree
metadata? Should I dig it from the BKCVS gateway, or is there a better
source? Where did you get the sparse git database from, Linus? (BTW, it
would be nice to get sparse.git with the directories as separate.)

  Have fun,

-- 
				Petr "Pasky" Baudis
Stuff: http://pasky.or.cz/
98% of the time I am right. Why worry about the other 3%.

Re: [ANNOUNCE] git-pasky-0.1

[Ingo Molnar]

* Petr Baudis <pasky@ucw.cz> wrote:

>   I will also need to do more testing on the linux kernel tree.
> Committing patch-2.6.7 on 2.6.6 kernel and then diffing results in
> 
> 	$ time gitdiff.sh `parent-id` `tree-id` >p
> 	real    5m37.434s
> 	user    1m27.113s
> 	sys     2m41.036s
> 
> which is pretty horrible, it seems to me. Any benchmarking help is of
> course welcomed, as well as any other feedback.

it seems from the numbers that your system doesnt have enough RAM for 
this and is getting IO-bound?

	Ingo

Re: [ANNOUNCE] git-pasky-0.1

[Willy Tarreau]

On Sun, Apr 10, 2005 at 07:33:49PM +0200, Ingo Molnar wrote:
> 
> * Petr Baudis <pasky@ucw.cz> wrote:
> 
> >   I will also need to do more testing on the linux kernel tree.
> > Committing patch-2.6.7 on 2.6.6 kernel and then diffing results in
> > 
> > 	$ time gitdiff.sh `parent-id` `tree-id` >p
> > 	real    5m37.434s
> > 	user    1m27.113s
> > 	sys     2m41.036s
> > 
> > which is pretty horrible, it seems to me. Any benchmarking help is of
> > course welcomed, as well as any other feedback.
> 
> it seems from the numbers that your system doesnt have enough RAM for 
> this and is getting IO-bound?

Not the only problem, without I/O, he will go down to 4m8s (u+s) which
is still in the same order of magnitude.

willy

Re: [ANNOUNCE] git-pasky-0.1

[Ingo Molnar]

* Willy Tarreau <willy@w.ods.org> wrote:

> > >   I will also need to do more testing on the linux kernel tree.
> > > Committing patch-2.6.7 on 2.6.6 kernel and then diffing results in
> > > 
> > > 	$ time gitdiff.sh `parent-id` `tree-id` >p
> > > 	real    5m37.434s
> > > 	user    1m27.113s
> > > 	sys     2m41.036s
> > > 
> > > which is pretty horrible, it seems to me. Any benchmarking help is of
> > > course welcomed, as well as any other feedback.
> > 
> > it seems from the numbers that your system doesnt have enough RAM for 
> > this and is getting IO-bound?
> 
> Not the only problem, without I/O, he will go down to 4m8s (u+s) which 
> is still in the same order of magnitude.

probably not the only problem - but if we are lucky then his system was 
just trashing within the kernel repository and then most of the overhead 
is the _unnecessary_ IO that happened due to that (which causes CPU 
overhead just as much). The dominant system time suggests so, to a 
certain degree. Maybe this is wishful thinking.

	Ingo

Re: Re: [ANNOUNCE] git-pasky-0.1

[Petr Baudis]

Dear diary, on Sun, Apr 10, 2005 at 07:45:12PM CEST, I got a letter
where Ingo Molnar <mingo@elte.hu> told me that...
> 
> * Willy Tarreau <willy@w.ods.org> wrote:
> 
> > > >   I will also need to do more testing on the linux kernel tree.
> > > > Committing patch-2.6.7 on 2.6.6 kernel and then diffing results in
> > > > 
> > > > 	$ time gitdiff.sh `parent-id` `tree-id` >p
> > > > 	real    5m37.434s
> > > > 	user    1m27.113s
> > > > 	sys     2m41.036s
> > > > 
> > > > which is pretty horrible, it seems to me. Any benchmarking help is of
> > > > course welcomed, as well as any other feedback.
> > > 
> > > it seems from the numbers that your system doesnt have enough RAM for 
> > > this and is getting IO-bound?
> > 
> > Not the only problem, without I/O, he will go down to 4m8s (u+s) which 
> > is still in the same order of magnitude.
> 
> probably not the only problem - but if we are lucky then his system was 
> just trashing within the kernel repository and then most of the overhead 
> is the _unnecessary_ IO that happened due to that (which causes CPU 
> overhead just as much). The dominant system time suggests so, to a 
> certain degree. Maybe this is wishful thinking.

It turns out to be the forks for doing all the cuts and such what is
bogging it down so awfully (doing diff-tree takes 0.48s ;-). I do about
15 forks per change, I guess, and for some reason cut takes a long of
time on its own.

I've rewritten the cuts with the use of bash arrays and other smart
stuff. I somehow don't feel comfortable using this and prefer the
old-fashioned ways, but it would be plain unusable without this.

Now I'm down to

	real    1m21.440s
	user    0m32.374s
	sys     0m42.200s

and I kinda doubt if it is possible to cut this much down. Almost no
disk activity, I have almost everything cached by now, apparently.

Anyway, you can git pull to get the optimized version.

Thanks for the help,

-- 
				Petr "Pasky" Baudis
Stuff: http://pasky.or.cz/
98% of the time I am right. Why worry about the other 3%.

Re: Re: [ANNOUNCE] git-pasky-0.1

[Linus Torvalds]

On Sun, 10 Apr 2005, Petr Baudis wrote:
> 
> It turns out to be the forks for doing all the cuts and such what is
> bogging it down so awfully (doing diff-tree takes 0.48s ;-). I do about
> 15 forks per change, I guess, and for some reason cut takes a long of
> time on its own.

Heh.

Can you pull my current repo, which has "diff-tree -R" that does what the 
name suggests, and which should be faster than the 0.48 sec you see..

It may not matter a lot, since actually generating the diff from the file 
contents is what is expensive, but remember my goal: I want the expense of 
a diff-tree to be relative to the size of the diff, so that implies that 
small diffs haev to be basically instantaenous. So I care.

So I just tried the 2.6.7->2.6.8 diff, and for me the new recursive
"diff-tree" can generate the _list_ of files changed in zero time:

	real    0m0.079s
	user    0m0.067s
	sys     0m0.024s

but then _doing_ the diff is pretty expensive (in this case 3800+ files
changed, so you have to unpack 7600+ objects - and even unpacking isn't
the expensive part, the expense is literally in the diff operation
itself).

Me, the stuff I automate is the small steps. Doing a single checkin. So
that's the case I care about going fast, when a "diff-tree" will likely
have maybe five files or something. That's why I want the small
incremental cases to go fast - it it takes me a minute to generate a diff
for a _release_, that's not a big deal. I make one release every other
month, but I work with lots of small patches all the time.

Anyway, with a fast diff-tree, you should be able to generate the list of 
objects for a fast "merge". That's next. 

(And by "merge", I of course mean "suck". I'm talking about the old CVS
three-way merge, and you have to specify the common parent explicitly and
it won't handle any renames or any other crud. But it would get us to 
something that might actually be useful for simple things. Which is why 
"diff-tree" is important - it gives the information about what to tell 
merge).

				Linus

Re: Re: Re: [ANNOUNCE] git-pasky-0.1

[Petr Baudis]

Dear diary, on Sun, Apr 10, 2005 at 10:38:11PM CEST, I got a letter
where Linus Torvalds <torvalds@osdl.org> told me that...
> On Sun, 10 Apr 2005, Petr Baudis wrote:
> > 
> > It turns out to be the forks for doing all the cuts and such what is
> > bogging it down so awfully (doing diff-tree takes 0.48s ;-). I do about
> > 15 forks per change, I guess, and for some reason cut takes a long of
> > time on its own.
> 
> Heh.
> 
> Can you pull my current repo, which has "diff-tree -R" that does what the 
> name suggests, and which should be faster than the 0.48 sec you see..

Funnily enough, now after some more cache teasing it's ~0.185. Your one
still ~0.17, though. :/ (That might be because of the format changes,
though, since you do less printing now.) (BTW, all those measurements
are done on my AMD K6 walking on 1600MHz, 512M RAM, about 200M available
for caches.)

Just out of interest, did you have a look at my diff-tree -r
implementation and decided that you don't like it, or you weren't aware
of it?

I will probably take most of your diff-tree change, but I'd prefer to do
the sha1->tree mapping directly in diff_tree().

> It may not matter a lot, since actually generating the diff from the file 
> contents is what is expensive, but remember my goal: I want the expense of 
> a diff-tree to be relative to the size of the diff, so that implies that 
> small diffs haev to be basically instantaenous. So I care.

Me too, of course.

> So I just tried the 2.6.7->2.6.8 diff, and for me the new recursive
> "diff-tree" can generate the _list_ of files changed in zero time:
> 
> 	real    0m0.079s
> 	user    0m0.067s
> 	sys     0m0.024s
> 
> but then _doing_ the diff is pretty expensive (in this case 3800+ files
> changed, so you have to unpack 7600+ objects - and even unpacking isn't
> the expensive part, the expense is literally in the diff operation
> itself).
> 
> Me, the stuff I automate is the small steps. Doing a single checkin. So
> that's the case I care about going fast, when a "diff-tree" will likely
> have maybe five files or something. That's why I want the small
> incremental cases to go fast - it it takes me a minute to generate a diff
> for a _release_, that's not a big deal. I make one release every other
> month, but I work with lots of small patches all the time.

I see.

> Anyway, with a fast diff-tree, you should be able to generate the list of 
> objects for a fast "merge". That's next. 
> 
> (And by "merge", I of course mean "suck". I'm talking about the old CVS
> three-way merge, and you have to specify the common parent explicitly and
> it won't handle any renames or any other crud. But it would get us to 
> something that might actually be useful for simple things. Which is why 
> "diff-tree" is important - it gives the information about what to tell 
> merge).

I currently already do a merge when you track someone's source - it will
throw away your previous HEAD record though, so if you committed some
local changes after the previous pull, you will get orphaned commits and
the changes will turn to uncommitted ones. I have some ideas regarding
how to do it properly (and do any arbitrary merging, for that matter), I
hope to get to it as soon as I catch up with you. :-)

BTW, the three-way merge comes from RCS. That reminds me, is there any
tool which will take .rej files and throw them into the file to create
rcsmerge-like conflicts? Perhaps it's fault of my bad tools, but I
prefer to work with the inline rejects much more to .rej files (except
to actually notice the rejects).

-- 
				Petr "Pasky" Baudis
Stuff: http://pasky.or.cz/
98% of the time I am right. Why worry about the other 3%.

Re: Re: Re: [ANNOUNCE] git-pasky-0.1

[Linus Torvalds]

On Mon, 11 Apr 2005, Petr Baudis wrote:
> 
> I currently already do a merge when you track someone's source - it will
> throw away your previous HEAD record though

Not only that, it doesn't do what I consider a "merge". 

A real merge should have two or more parents. The "commit-tree" command
already allows that: just add any arbitrary number of "-p xxxxxxxxx"  
switches (well, I think I limited it to 16 parents, but that's just a
totally random number, there's nothing in the file format or anything 
else that limits it).

So while you've merged my "data", but you've not actually merged my
revision history in your tree.

And the reason a real merge _has_ to show both parents properly is that 
unless you do that, you can never merge sanely another time without 
getting lots of clashes from the previous merge. So it's important that a 
merge really shows both trees it got data from.

This is, btw, also the reason I haven't merged with your tree - I want to 
get to the point where I really _can_ merge without throwing away the 
information. In fact, at this point I'd rather not merge with your tree at 
all, because I consider your tree to be "corrupt" thanks to lacking the 
merge history.

So you've done the data merge, but not the history merge.

And because you didn't do the history merge, there's no way to
automatically find out what point of my tree you merged _with_. See?

And since I have no way to see what point in time you merged with me, now
I can't generate a nice 3-way diff against the last common ancestor of
both of our trees.

So now I can't do a three-way merge with you based on any sane ancestor,
unless I start guessing which ancestor of mine you merged with. Now, that
"guess" is easy enough to do with a project like "git" which currently has
just a few tens of commits and effectively only two parallell development
trees, but the whole point is to get to a system where that isn't true..

			Linus

Re: Re: Re: Re: [ANNOUNCE] git-pasky-0.1

[Petr Baudis]

Dear diary, on Mon, Apr 11, 2005 at 01:10:58AM CEST, I got a letter
where Linus Torvalds <torvalds@osdl.org> told me that...
> 
> 
> On Mon, 11 Apr 2005, Petr Baudis wrote:
> > 
> > I currently already do a merge when you track someone's source - it will
> > throw away your previous HEAD record though
> 
> Not only that, it doesn't do what I consider a "merge". 
> 
> A real merge should have two or more parents. The "commit-tree" command
> already allows that: just add any arbitrary number of "-p xxxxxxxxx"  
> switches (well, I think I limited it to 16 parents, but that's just a
> totally random number, there's nothing in the file format or anything 
> else that limits it).
> 
> So while you've merged my "data", but you've not actually merged my
> revision history in your tree.

Well, that's exactly what I was (am) going to do. :-) That's also why I
said that I (virtually) throw the local commits away now. Instead, if
there were any local commits, I will do git merge:

	commit-tree $(write-tree) -p $local_head -p $tracked_tree

Note that I will need to make this two-phase - first applying the
changes, then doing the commit; between those two phases, the user
should resolve potential conflicts and check if the merge went right.

I think I will name the first phase git merge and the second phase will
be just git commit, and I will store the merge information in
.dircache/. (BTW, I think the directory name is pretty awful; what about
.git/ ?)

> And the reason a real merge _has_ to show both parents properly is that 
> unless you do that, you can never merge sanely another time without 
> getting lots of clashes from the previous merge. So it's important that a 
> merge really shows both trees it got data from.
> 
> This is, btw, also the reason I haven't merged with your tree - I want to 
> get to the point where I really _can_ merge without throwing away the 
> information. In fact, at this point I'd rather not merge with your tree at 
> all, because I consider your tree to be "corrupt" thanks to lacking the 
> merge history.
> 
> So you've done the data merge, but not the history merge.
> 
> And because you didn't do the history merge, there's no way to
> automatically find out what point of my tree you merged _with_. See?
> 
> And since I have no way to see what point in time you merged with me, now
> I can't generate a nice 3-way diff against the last common ancestor of
> both of our trees.
> 
> So now I can't do a three-way merge with you based on any sane ancestor,
> unless I start guessing which ancestor of mine you merged with. Now, that
> "guess" is easy enough to do with a project like "git" which currently has
> just a few tens of commits and effectively only two parallell development
> trees, but the whole point is to get to a system where that isn't true..

Well, I've wanted to get the basic things working first before doing git
merge. (Especially since until recently, diff-tree was PITA to work
with, and before that it didn't even exist.) If you want, I can rebuild
my tree with doing the merging properly, after I have git merge working.

(BTW, it would be useful to have a tool which just blindly takes what
you give it on input and throws it to an object of given type; I will
need to construct arbitrary commits during the rebuild if I'm to keep
the correct dates.)

-- 
				Petr "Pasky" Baudis
Stuff: http://pasky.or.cz/
98% of the time I am right. Why worry about the other 3%.

Re: Re: Re: Re: [ANNOUNCE] git-pasky-0.1

[Linus Torvalds]

On Mon, 11 Apr 2005, Petr Baudis wrote:
> 
> (BTW, it would be useful to have a tool which just blindly takes what
> you give it on input and throws it to an object of given type; I will
> need to construct arbitrary commits during the rebuild if I'm to keep
> the correct dates.)

Hah. That's what "COMMITTER_NAME" "COMMITTER_EMAIL" and "COMMITTER_DATE" 
are there for.

There's two things to commits: when (and by whom) it was committed to a
tree, and when the changes were really done.

So set the COMMITTER_xxx things to the person/time you want to consider 
the _original_ one, and let "commit-tree" author you as the creator of the 
commit itself. The regular "ChangeLog" thing should only show the author 
and original time, but it's nice to see who created the commit itself.

I did this very much on purpose: see how I always try to attribute 
authorship in BK to the person who actually wrote the code. At the same 
time, I think it's interesting from a tracking standpoint to also see 
when/where that change got introduced into a tree.

I _tried_ to get this right in the sparse tree conversion. I won't 
guarantee that it's all correct, but the top commit in the sparse tree 
looks like this:

	tree 67607f05a66e36b2f038c77cfb61350d2110f7e8
	parent 9c59995fef9b52386e5f7242f44720a7aca287d7
	author Christopher Li <sparse@chrisli.org> Sat Apr  2 09:30:09 PST 2005
	committer Linus Torvalds <torvalds@ppc970.osdl.org> Thu Apr  7 20:06:31 2005

	...

exactly because I tracked when I committed it to the sparse tree 
_separately_ from tracking when it was created.

So when I re-create the sparse-tree, I'll also end up re-writing the 
"committer" information. And that's proper. That's really saying "this 
sha1 object was created by Xxxx at time Xxxx".

Btw, the "COMMITTER_xxxx" environment variables are very confusingly
named. They actually go into the _author_ line in the commit object. I'm a
total retard, and I really don't know why I called it "COMMITTER_xxx"  
instead of "AUTHOR_xxx".

			Linus "retard" Torvalds

Re: Re: Re: Re: Re: [ANNOUNCE] git-pasky-0.1

[Petr Baudis]

Dear diary, on Mon, Apr 11, 2005 at 01:46:50AM CEST, I got a letter
where Linus Torvalds <torvalds@osdl.org> told me that...
> 
> 
> On Mon, 11 Apr 2005, Petr Baudis wrote:
> > 
> > (BTW, it would be useful to have a tool which just blindly takes what
> > you give it on input and throws it to an object of given type; I will
> > need to construct arbitrary commits during the rebuild if I'm to keep
> > the correct dates.)
> 
> Hah. That's what "COMMITTER_NAME" "COMMITTER_EMAIL" and "COMMITTER_DATE" 
> are there for.
> 
> There's two things to commits: when (and by whom) it was committed to a
> tree, and when the changes were really done.
> 
> So set the COMMITTER_xxx things to the person/time you want to consider 
> the _original_ one, and let "commit-tree" author you as the creator of the 
> commit itself. The regular "ChangeLog" thing should only show the author 
> and original time, but it's nice to see who created the commit itself.

I already use those - look at my ChangeLog. (That's because for certain
reasons I'm working on git in a half-broken chrooted environment.)

When rebuilding the tree from scratch, I wanted like to do it
transparently - that is, so that noone could notice that I rebuilt it,
since it effectively still _is_ the original tree from the data
standpoint, just the history flow is actually correct this time.

> Btw, the "COMMITTER_xxxx" environment variables are very confusingly
> named. They actually go into the _author_ line in the commit object. I'm a
> total retard, and I really don't know why I called it "COMMITTER_xxx"  
> instead of "AUTHOR_xxx".

So, who will fix it in his tree first! ;-)

-- 
				Petr "Pasky" Baudis
Stuff: http://pasky.or.cz/
98% of the time I am right. Why worry about the other 3%.

GIT license (Re: Re: Re: Re: Re: [ANNOUNCE] git-pasky-0.1)

[Linus Torvalds]

Btw, does anybody have strong opinions on the license? I didn't put in a 
COPYING file exactly because I was torn between GPLv2 and OSL2.1.

I'm inclined to go with GPLv2 just because it's the most common one, but I 
was wondering if anybody really had strong opinions. For example, I'd 
really make it "v2 by default" like the kernel, since I'm sure v3 will be 
fine, but regardless of how sure I am, I'm _not_ a gambling man.

		Linus

Re: GIT license (Re: Re: Re: Re: Re: [ANNOUNCE] git-pasky-0.1)

[Petr Baudis]

Dear diary, on Mon, Apr 11, 2005 at 02:20:52AM CEST, I got a letter
where Linus Torvalds <torvalds@osdl.org> told me that...
> Btw, does anybody have strong opinions on the license? I didn't put in a 
> COPYING file exactly because I was torn between GPLv2 and OSL2.1.
> 
> I'm inclined to go with GPLv2 just because it's the most common one, but I 
> was wondering if anybody really had strong opinions. For example, I'd 
> really make it "v2 by default" like the kernel, since I'm sure v3 will be 
> fine, but regardless of how sure I am, I'm _not_ a gambling man.

Oh, I wanted to ask about this too. I'd mostly prefer GPLv2 (I have no
problem with the version restriction, I usually do it too), it's the one
I'm mostly familiar with and OSL appears to be incompatible with GPL (at
least FSF says so about OSL1.0), which might create various annoying
issues. I hate when licenses get in my way and prevent me to possibly
include some useful code.

-- 
				Petr "Pasky" Baudis
Stuff: http://pasky.or.cz/
98% of the time I am right. Why worry about the other 3%.

Re: GIT license (Re: Re: Re: Re: Re: [ANNOUNCE] git-pasky-0.1)

[Ingo Molnar]

* Linus Torvalds <torvalds@osdl.org> wrote:

> Btw, does anybody have strong opinions on the license? I didn't put in 
> a COPYING file exactly because I was torn between GPLv2 and OSL2.1.
> 
> I'm inclined to go with GPLv2 just because it's the most common one, 
> but I was wondering if anybody really had strong opinions. For 
> example, I'd really make it "v2 by default" like the kernel, since I'm 
> sure v3 will be fine, but regardless of how sure I am, I'm _not_ a 
> gambling man.

is there any fundamental problem with going with v2 right now, and then 
once v3 is out and assuming it looks ok, all newly copyrightable bits 
(new files, rewrites, substantial contributions, etc.) get a v3 
copyright? (and the collection itself would be v3 too) That method 
wouldnt make it fully v3 automatically once v3 is out, but with time 
there would be enough v3 bits in it to make it essentially v3. This way 
we wouldnt have to blanket trust v3 before having seen it, and wouldnt 
be stuck at v2 either.

	Ingo

Re: GIT license (Re: Re: Re: Re: Re: [ANNOUNCE] git-pasky-0.1)

[Florian Weimer]

* Ingo Molnar:

> is there any fundamental problem with going with v2 right now, and then 
> once v3 is out and assuming it looks ok, all newly copyrightable bits 
> (new files, rewrites, substantial contributions, etc.) get a v3 
> copyright? (and the collection itself would be v3 too) That method 
> wouldnt make it fully v3 automatically once v3 is out, but with time 
> there would be enough v3 bits in it to make it essentially v3.

Almost certainly, v3 will be incompatible with v2 because it adds
further restrictions.  This means that your proposal would result in
software which is not redistributable by third parties.

Re: Re: GIT license (Re: Re: Re: Re: Re: [ANNOUNCE] git-pasky-0.1)

[Petr Baudis]

Dear diary, on Mon, Apr 11, 2005 at 10:40:00AM CEST, I got a letter
where Florian Weimer <fw@deneb.enyo.de> told me that...
> * Ingo Molnar:
> 
> > is there any fundamental problem with going with v2 right now, and then 
> > once v3 is out and assuming it looks ok, all newly copyrightable bits 
> > (new files, rewrites, substantial contributions, etc.) get a v3 
> > copyright? (and the collection itself would be v3 too) That method 
> > wouldnt make it fully v3 automatically once v3 is out, but with time 
> > there would be enough v3 bits in it to make it essentially v3.
> 
> Almost certainly, v3 will be incompatible with v2 because it adds
> further restrictions.  This means that your proposal would result in
> software which is not redistributable by third parties.

Hmm, what would be actually the point in introducing further
restrictions? Anyone who then wants to get around them will just
distribute the software with the "any later version" provision under
GPLv2, and GPLv3 will have no impact expect for new software with "v3 or
any later version" provision. What am I missing?

I've been doing a lot of LKML catching up, and I remember someone
suggesting using GPLv2 (for kernel, but should apply to git too), with a
provision to let someone trusted (Linus) decide when GPLv3 is out
whether you can use GPLv3 for the kernel too. Does it make sense? And is
it even legally doable without sending signed written documents to
Linus' tropical hacienda?

-- 
				Petr "Pasky" Baudis
Stuff: http://pasky.or.cz/
98% of the time I am right. Why worry about the other 3%.

Re: GIT license (Re: Re: Re: Re: Re: [ANNOUNCE] git-pasky-0.1)

[Florian Weimer]

* Petr Baudis:

>> Almost certainly, v3 will be incompatible with v2 because it adds
>> further restrictions.  This means that your proposal would result in
>> software which is not redistributable by third parties.
>
> Hmm, what would be actually the point in introducing further
> restrictions? Anyone who then wants to get around them will just
> distribute the software with the "any later version" provision under
> GPLv2, and GPLv3 will have no impact expect for new software with "v3 or
> any later version" provision. What am I missing?

Software continues to evolve.  The copyright owners can relicense the
code base under v3, and use v3 for all subsequent changes to the
software.  The trouble with relicensing is that you have to contact
all copyright holders (or remove their code).  This tends to be
impossible in long-running projects without contractual agreements
between the developers.