Switching to Git?

Switching to Git?

[Ludovic Courtès]

Hi,

How about switching from CVS to Git [0]?

What this would bring us:

  * Decentralized Development

    As you may know, this would allow every interested user to hack on
    their side, pulling changes from the main repository as they see
    fit, and promoting their changes whenever they want.  This is really
    appreciable.

  * Off-Line Operation

    As a corollary, this would allow off-line operation on the local
    copy of the repository.

  * Speed and Bandwidth Improvement

    Git operates on a local repository, which makes operations very
    fast.  This is a significant change when one has got used to waiting
    for "cvs diff" to complete for ages.  ;-)

  * Transactional, Changeset-Oriented

    Commit operations are transactional and changeset-oriented.  Changes
    to a collection of files that are committed at the same time do
    appear as a single "change set", rather than as separate changes as
    with CVS.  This means that GNU-style change logs can be generated
    automatically using tools like `git2cl' [4].

  * Nice Web Interface

    See [1] for example.


These are the most obvious benefits.

Note that Git is now supported on Savannah [2].  It's used by various
GNU projects, and also non-GNU projects (one of which is quite famous
;-)).

Han-Wen did a full import of the CVS history into Git some time ago [1].
Note that it preserves tags and branches.  This Git repository is kept
in sync with CVS using a cron job that runs on Han-Wen's machine.
However, it is not automatically synchronized in the other direction,
making it inconvenient.

Of course, nothing's black and white and Git has some weaknesses, too.
Most notably, its UI is a bit rough and at least not to everyone's taste
(which can be worked around by using companion tools such as Cogito
[3]).

Opinions?

Thanks,
Ludovic.

[0] http://git.or.cz/
[1] http://repo.or.cz/w/guile.git
[2] http://git.sv.gnu.org/
[3] http://git.or.cz/cogito/
[4] http://repo.or.cz/w/git2cl.git/



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Re: Switching to Git?

[Kevin Ryde]

ludo@gnu.org (Ludovic Courtès) writes:
>
> How about switching from CVS to Git [0]?

I would say no.  All these other revision systems seem to come and go,
but their supposed features rarely seem to justify the learning curve
(the frequently steep, time consuming, and frustrating curve :-).

>     waiting for "cvs diff" to complete for ages.  ;-)

Emacs can work offline for diffs, for the most part.  (I never had much
joy when it merges, but I'm sure someone must have set it up to update
its cached current copy.)

>     This means that GNU-style change logs can be generated
>     automatically using tools like `git2cl' [4].

Bit overrated those things, the output always seems pretty ordinary.
I suppose of course nobody's forced to use it though.


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Re: Switching to Git?

[Ludovic Courtès]

ludovic.courtes@laas.fr (Ludovic Courtès) writes:

> I see that Emacs (which still uses CVS as its primary RCS) has a Git
> mirror at Savannah.  If Savannah people can do this for us, that'd be a
> good compromise, I think, as long as it allows people to use either CVS
> or Git without interfering.

Alas, it's a read-only mirror:

  http://www.mail-archive.com/savannah-hackers-public@gnu.org/msg00921.html

(Interesting message on the topic of migration, BTW.)

Thanks,
Ludovic.



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Re: Switching to Git?

[Dan McMahill]

Ludovic Courtès wrote:
> Git's basic command set is really close to that of CVS.  I recommend
> that you look at this document:
> 
>   http://git.or.cz/course/cvs.html
> 
> (It's about Cogito, a tool built on top of Git, but for most commands
> you could substitute `git' to `cg'.)

yeah, but cogito is dead.  The maintainer says so.  Also cogito really 
doesn't work on solaris.  I don't know about other non-linux os's.

-Dan




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Re: Switching to Git?

[Han-Wen Nienhuys]

Kevin Ryde escreveu:
> ludo@gnu.org (Ludovic Courtès) writes:
>> How about switching from CVS to Git [0]?
> 
> I would say no.  All these other revision systems seem to come and go,
> but their supposed features rarely seem to justify the learning curve
> (the frequently steep, time consuming, and frustrating curve :-).
> 
>>     waiting for "cvs diff" to complete for ages.  ;-)
> 
> Emacs can work offline for diffs, for the most part.  (I never had much
> joy when it merges, but I'm sure someone must have set it up to update
> its cached current copy.)

I think you don't appreciate the power of Git in this respect. Emacs can do
the diff of your checkout and HEAD locally.  The neat thing of Git is that 
you can actually do a cvs-annotate offline, tracking the origin of each line 
of code.

>>     This means that GNU-style change logs can be generated
>>     automatically using tools like `git2cl' [4].
> 
> Bit overrated those things, the output always seems pretty ordinary.
> I suppose of course nobody's forced to use it though.

GNU style ChangeLogs are pointless with git.  git-log basically 
offers the same information, and with gitk you get a graphical interface
combining commit messages, diffs and file tree-views 

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Re: Switching to Git?

[Greg Troxel]

[I've been using CVS since 1994 and have seen more VC systems come and
go than I can remember.  So I'm predisposed to be cranky about
switching.]

My quick reaction is that this would be be good overall.  While the
benefits are probably significant, switching makes it harder for people
to follow along.  I say this because of my experience with guile-gnome -
they have changed revision control systems several times and I have had
trouble with each one.  I no longer track guile-gnome HEAD - just update
pkgsrc to releases and then complain when the latest release doesn't
work with the latest release of some dependency.

The more serious problem with guile is a lack of focus on timely, stable
releases usable by people who want to integrate it.  Plus backwards
compatibility so that people that do integrated it have very little
grief, and the current slib mess.

I wonder if the 'decentralized development' notion is really consistent
with the "papers, please" demand of FSF.  Have "assigned" projects used
distributed CM systems?  How has that been handled?

But if the people that have assigned changes and actually hack on guile
(which isn't me) want to use git, and if it will help the cause of
better releases that can be used in confidence, then that seems fine.


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Re: Switching to Git?

[Han-Wen Nienhuys]

Greg Troxel escreveu:
> The more serious problem with guile is a lack of focus on timely, stable
> releases usable by people who want to integrate it.  Plus backwards
> compatibility so that people that do integrated it have very little
> grief, and the current slib mess.

I have switched from CVS to Git for lilypond development, and it has done wonders
for my stable releases. Since it is extremely easy to cherry-pick patches 
between branches, I back/front port all bugfixes.  The releases are even
synced: 2.11.29 contains fixes and features, and where possible the same
fixes appear in 2.10.29 (stable version)

> I wonder if the 'decentralized development' notion is really consistent
> with the "papers, please" demand of FSF.  Have "assigned" projects used
> distributed CM systems?  How has that been handled?

Decentralized development is a policy decision, and centralized is just as 
well possible with git. Even more so, because you can actually track the 
the author (the person writing the patch) separately from the committer 
(person having write access to the repository).  This makes tracking the
copyright status (ie. who wrote what) of a project much more transparent.

-- 
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Re: Switching to Git?

[Dan McMahill]

Ludovic Courtès wrote:

> Of course, nothing's black and white and Git has some weaknesses, too.
> Most notably, its UI is a bit rough and at least not to everyone's taste
> (which can be worked around by using companion tools such as Cogito
> [3]).
> 
> Opinions?
> 
> Thanks,
> Ludovic.
> 
> [0] http://git.or.cz/
> [1] http://repo.or.cz/w/guile.git
> [2] http://git.sv.gnu.org/
> [3] http://git.or.cz/cogito/
> [4] http://repo.or.cz/w/git2cl.git/

cogito is dead.  And on top of that, cogito would need a good bit of 
hacking to really make it portable anyway.

Another project I'm on has switched to git from cvs and I'm bringing up 
the rear in terms of trying to learn the tool enough to use it without 
making a mess of things.  My biggest complaint, aside from having to 
learn another tool, is that git is not really a lightweight tool for 
some systems.  For example, if you're on solaris you can get cvs from 
the software supplement cd (or whatever that cd is called) and you're 
ready to go.  With git I think you're still building from source and you 
need perl, python, tcl/tk, expat, and curl.  On top of that, git uses a 
homebrew build systems that just doesn't work out of the box on all 
systems.  Luckily I was able to install git via netbsd's pkgsrc on my 
solaris box but without pkgsrc it would have been moderately painful.

I still haven't used git enough to form an opinion on the user side.

-Dan


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Re: Switching to Git?

[Han-Wen Nienhuys]

Dan McMahill escreveu:
> Another project I'm on has switched to git from cvs and I'm bringing up
> the rear in terms of trying to learn the tool enough to use it without
> making a mess of things.  My biggest complaint, aside from having to
> learn another tool, is that git is not really a lightweight tool for
> some systems.  For example, if you're on solaris you can get cvs from
> the software supplement cd (or whatever that cd is called) and you're
> ready to go.  With git I think you're still building from source and you
> need perl, python, tcl/tk, expat, and curl.  On top of that, git uses a
> homebrew build systems that just doesn't work out of the box on all
> systems.  Luckily I was able to install git via netbsd's pkgsrc on my
> solaris box but without pkgsrc it would have been moderately painful.

This is unfortunate. However, if you're interested, I can try to build
a cross-compile for solaris (I maintain a half-baked mingw Git version,
I could add solaris too). 


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Re: Switching to Git?

[Andy Wingo]

Bon soir Msr Courtès !

ludo@gnu.org (Ludovic Courtès) writes:

> How about switching from CVS to Git [0]?

The advantages you list are compelling. It is especially good that
savannah supports git. I have only two points to counter: (1) git sucks
to use (but somehow many people seem to manage), and (2) git does not
work on windows.

As another poster mentioned, cogito is not where it's at.

Particularly the second point is a bit troubling. 

How about switching from CVS to bzr? I ask in jest almost, but I think
it is a worthwhile option.

As an aside, in GStreamer we are going to completely punt on this
question, and switch to subversion. You get changesets, which allows
git-svn, bzr-svn, etc, which are not bad options. That could be the
correct switch for guile -- there is no downside to switching to
subversion relative to CVS.

Regards,

Andy.
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Re: Switching to Git?

[Cesar Strauss]

Andy Wingo wrote:

> (2) git does not  work on windows.

Not entirely true. I do use git on Windows, courtesy of the Cygwin
project. I use it even for native MinGW projects.

> ludo@gnu.org (Ludovic Courtès) writes:
> 
>> How about switching from CVS to Git [0]?

As a user, what I like most about git is its integrated graphical
history browser (gitk). It offers the same functionality as the
web-based interface, only much faster, because all history is cached on
disk. For one particular project, I could even unsubscribe myself from
the commit notification mailing list, after the project switched to git.

Regards,
Cesar



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Re: Switching to Git?

[Han-Wen Nienhuys]

Andy Wingo escreveu:
>> How about switching from CVS to Git [0]?
> 
> The advantages you list are compelling. It is especially good that
> savannah supports git. I have only two points to counter: (1) git sucks
> to use (but somehow many people seem to manage), and (2) git does not
> work on windows.

This is not true. There is a mingw port, which is starting to become usable.
However, I'm a bit mystified why windows support should be a priority for 
GUILE.

As for the user interface, it does have it's edges, but after a couple of
weeks it feels quite natural for common stuff (committing, pulling, pushing,
merging).  I do have to look at the manual for the more exotic commands 
(rebase, pickaxe, etc.)

> As an aside, in GStreamer we are going to completely punt on this
> question, and switch to subversion. You get changesets, which allows
> git-svn, bzr-svn, etc, which are not bad options. That could be the
> correct switch for guile -- there is no downside to switching to
> subversion relative to CVS.

Frankly, I think it's nuts not to go with a distributed system if 
transitioning away from CVS.  The only pertinent question is git or
mercurial. 


-- 
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Re: Switching to Git?

[Han-Wen Nienhuys]

Ludovic Courtès escreveu:
 
> Han-Wen did a full import of the CVS history into Git some time ago [1].
> Note that it preserves tags and branches.  This Git repository is kept
> in sync with CVS using a cron job that runs on Han-Wen's machine.

Note that I messed up the name conversion in the history. If we go this route,
the conversion should be redone; it's not a big deal, it only takes a couple 
hours.



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Re: Switching to Git?

[Rob Browning]

ludo@gnu.org (Ludovic Courtès) writes:

> Hi,
>
> How about switching from CVS to Git [0]?

I'd probably lean in favor.  I've tried quite a few of the RCS
systems[1], and I now use git for all my local work.  So far, I've
been extremely pleased, though I haven't yet used it heavily when
working with others.

Also, my impression is that the core git commands are much more
friendly these days, so anyone who tried them a while back and was
discouraged might want to take another look.

[1] cvs -> svn -> tla -> baz -> bzr -> hg -> git

-- 
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Re: Switching to Git?

[dsmich]

---- Andy Wingo <wingo@pobox.com> wrote: 
> ludo@gnu.org (Ludovic Courtès) writes:
> > How about switching from CVS to Git [0]?
 
> As an aside, in GStreamer we are going to completely punt on this
> question, and switch to subversion. You get changesets, which allows
> git-svn, bzr-svn, etc, which are not bad options. That could be the
> correct switch for guile -- there is no downside to switching to
> subversion relative to CVS.

If there must be a switch, I'd also say that subversion is probably the best way to go.  Less culture shock for long time cvs users.  Windows people aren't left out.  Guile doesn't really need the massively distributed model that the Linux kernel requires.

My $0.02

-Dale



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Re: Switching to Git?

[Han-Wen Nienhuys]

dsmich@adelphia.net escreveu:
> If there must be a switch, I'd also say that subversion is probably the best way to go. 
> Less culture shock for long time cvs users.  Windows people aren't left out.  Guile doesn't
> really need the massively distributed model that the Linux kernel requires.

Actually, try this for a data point:

 git clone git://git.sv.gnu.org/lilypond.git
 cd lilypond; gitk

what you will see is the history of LilyPond, which is not massively distributed
by any standard. If you press page down a couple of time, you will see 'parallel'
development and merging of several topics, eg.

 - Spacing features by Joe Neeman
 - Release fixes by me
 - translation updates by John Mandereau and helpers
 - doc updates by Graham Percival and helpers

these all happen in parallel. In particular, I am the release coordinator,
and I always make releases which are effectively branches. This means that 
I can make small fixes (eg. a make dist failure) to build a release locally
and merge them back into the repository HEAD later. My releases are 
not inconvenienced by large hacks that are pushed to the HEAD. 


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