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Linus on GIT and SCM 392

Posted by kdawson
from the strong-opinions dept.
An anonymous reader sends us to a blog posting (with the YouTube video embedded) about Linus Torvalds' talk at Google a few weeks back. Linus talked about developing GIT, the source control system used by the Linux kernel developers, and exhibited his characteristic strong opinions on subjects around SCM, by which he means "Source Code Management." SCM is a subject that coders are either passionate about or bored by. Linus appears to be in the former camp. Here is his take on Subversion: "Subversion has been the most pointless project ever started... Subversion used to say, 'CVS done right.' With that slogan there is nowhere you can go. There is no way to do CVS right."
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Linus on GIT and SCM

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  • Source Safe (Score:5, Funny)

    by EraserMouseMan (847479) on Saturday June 02, 2007 @10:25PM (#19367699)
    Well Linus didn't have anything bad to say about MS Source Safe. . .

    [ducking] Sorry, I couldn't resist the urge. ;-)
    • by HaeMaker (221642) on Saturday June 02, 2007 @10:46PM (#19367819) Homepage
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      aaaaaaaf
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      1,712,928 Files...
  • Why winge? (Score:5, Funny)

    by gilesjuk (604902) <giles.jones@NOspam.zen.co.uk> on Saturday June 02, 2007 @10:31PM (#19367737)
    CVS and Subversion are open source projects, Linus should fix them.
    • Re:Why winge? (Score:4, Insightful)

      by Brandybuck (704397) on Saturday June 02, 2007 @10:36PM (#19367757) Homepage Journal
      The problem with CVS and Subversion are one of fundamental design. At least, that is what Linus is suggesting. You can't fix them without rewriting them completely from the ground up.
      • Re: (Score:3, Interesting)

        by DrXym (126579)
        I don't think there is anything especially wrong with Subversion. Sure it doesn't support changesets which is an very handy feature if you're juggling lots of checkins, or your role is release engineer but it is possible to work without them, e.g. using patches and atomic fileset commits. I used CMVC with changesets and it is useful for release managed projects but its bit of a pain for casual or self-managed code.

        Other features such as replication would also be useful if svn were a slug but it isn't. Som

      • Re: (Score:3, Informative)

        by bensch128 (563853)
        SCMs like SVN and perforce are fundamentally different from GIT, darcs and bzr.

        SVN and perforce are centralized SCMs and GIT,darcs,bzr are decentralized.
        So SVN,CVS,Perforce are uninteresting to Linus because he and the linux kernel developers work in a decentralized manner. Working decentralized means that there needs to be a person to receive patches from others and apply it to his tree. Anyone with write permissions can commit to a SVN server without submitting patches to a manager. Both have their own pl
        • Re: (Score:3, Informative)

          by imp (7585)
          I've use perforce to keep a private FreeBSD branch for about 6 years now. It just works. I've done enough commits that come from that branch (and about 6 others) to FreeBSD to stay in the top 5 kernel developers for most of that time. Perforce absolutely rocks in helping to keep me sane.

          While it is centralized, one cannot deny that its branch merging tools are about the most powerful out there.

          Warner Losh
          FreeBSD kernel hacker

          P.S. This is an abbreviated version of a much longer post to the blog listed in
    • Re:Why winge? (Score:5, Insightful)

      by zzatz (965857) on Saturday June 02, 2007 @10:47PM (#19367821)
      Linus isn't saying that CVS and Subversion have fixable bugs or missing features. It's not about the code.

      He is saying that they solve the wrong problem. The Subversion team wants to solve Problem A, and Linus wants to solve Problem B. No amount of code will turn the solution to Problem A into a solution for Problem B. Bothering the Subversion team with code addressing Problem B will only irritate them, since they're working on Problem A.

      The right way to handle differing goals is to start a different project. That's what he did.

      Don't be confused by the labels. Source Code Management means different things to different people, and there isn't always much overlap in how each person defines it. Ships and airplanes are both 'vehicles', but that doesn't mean that a few changes will turn one to the other.
      • Re:Why winge? (Score:4, Insightful)

        by Eil (82413) on Sunday June 03, 2007 @02:24PM (#19372775) Homepage Journal
        Linus isn't saying that CVS and Subversion have fixable bugs or missing features. It's not about the code.

        I think it's more about bashing some thing or another to gain attention.

        I liked Linus, and I've held him in high regard for more than a decade for all that he's helped accomplished while still being mostly modest about it. But he seems to be slowly evolving into another Stallman lately. Everything has been, "I don't like x and therefore x is stupid and you're a mentally-retarded asshat if you don't agree with everything I say."

        Just last week he started a flamewar on LKML about software suspend. Linus threw a shitfit when some bugs in suspend-to-disk were affecting suspend-to-RAM. After insulting a few other kernel developers without provocation, he basically ended the conversation by saying that the whole thing was going to be ripped out and redone only as suspend-to-RAM because he didn't use suspend-to-disk. Since he himself didn't use it, he postulated that it was a completely useless waste of time for anyone to implement it.

        The Subversion team wants to solve Problem A, and Linus wants to solve Problem B.

        So why couldn't he have simply said, "GIT solves the problem that I need it to solve, which is different from Subversion's"? Oh, right, because that wouldn't be interesting enough to make the front page of Slashdot. Too bad if the alternative alienates the half of the open source community that likes Subversion for what it does.
    • Re:Why winge? (Score:5, Informative)

      by RedWizzard (192002) on Saturday June 02, 2007 @10:49PM (#19367829)

      CVS and Subversion are open source projects, Linus should fix them.
      He did fix them: he wrote GIT. He's no really whinging, he's saying "I wrote this tool because the other options are crap".
  • how to learn git? (Score:5, Informative)

    by zojas (530814) <kevin@astrophoenix.com> on Saturday June 02, 2007 @10:36PM (#19367759) Homepage
    I've tried to use git, and I feel like if you want to do anything more than commit, you have to jump off a cliff which has serious spikes at the bottom. seriously, if you want to learn how to do more than 1 or 2 of the simplest operations with it, you have to invest serious time. I tried, and never could get there.

    anybody have a good tutorial? (not the crappy one which comes with it)

    I'm not an SCM rube either. I've competently used tla (arch), darcs, and of course CVS. but git just seems too hard to use. damn fast though.

    • I've tried to use git, and I feel like if you want to do anything more than commit, you have to jump off a cliff which has serious spikes at the bottom. seriously, if you want to learn how to do more than 1 or 2 of the simplest operations with it, you have to invest serious time. I tried, and never could get there.

      It was hard to write...it should be hard to use...errr... this is Linus we're talking about, right?
    • My favorite, of course, is Mercurial [selenic.com]. My main draw is that I had been interested in distributed SCMs for years, but had never found one that made any sense to me whatsoever. I was on the hunt again and stumbled on Mercurial, and I've been hooked ever since.

      Of the various distributed SCMs, Mercurial is the easiest to use one I've found. And it's pretty fast, though not quite as fast as git (though I have some ideas on how to fix that). And since it's written in Python with only a very small C component it runs on many platforms.

    • Re:how to learn git? (Score:5, Informative)

      by Anonymous Coward on Saturday June 02, 2007 @11:28PM (#19368025)

      # set up new project
      cd project
      git init
      git add .
      git commit -a -m "Initial commit"
       
      # edit a file
      vi file.php
      git commit -a
       
      # add a file
      vi new.php
      git add new.php
      git commit -a
       
      # see the log
      git log
       
      # make a branch
      git branch working
      git checkout working
      # or in one step
      git checkout -b working
       
      # add some changes to this branch
      vi file.php
       
      # see what you changed
      git status
       
      # check it in
      git commit -a
       
      # see all branches
      git branch
       
      # go back to the first branch (initial branch is called "master" by default)
      git checkout master
       
      # make some other changes
      vi other.php
      git commit -a
       
      # merge the working branch into this one
      git merge working
       
      # see the branches and merges in a graphical browser
      gitk --all
       
      # let's do a log of all commits in "working" that don't exist in "master"
      git log master..working
       
      # hmm let's undo that last merge (tip of branch is HEAD, one commit back is HEAD^.. we are "popping" one commit)
      git reset --hard HEAD^
       
      # push your changes out (push the tip of local "master" branch to remote "incoming" branch)
      git push foo.bar.com:~/myrepo master:incoming
       
      # pull changes from another repo (remote "feature1" into local "feature1" branch)
      git pull baz.bar.com:~/otherrepo feature1
       
      # move the branch point of the "working" branch to the top of the "master" branch
      git checkout working
      git rebase master
      It can get a LOT more complex of course.

      When you're starting out, just remember "git commit -a" and you'll be fine. Also check out "git reflog" to see the linear history of your repo. The pulling/pushing stuff can get a lot more complex but it's damn powerful. If you can figure out Arch (yeesh) you can figure out git!

      SLASHDOT SEZ: you have too few characters per line. Okay, slashdot, here's part of the man page for git-rebase:

      If is specified, git-rebase will perform an automatic git checkout before doing anything else. Otherwise it remains on the current branch. All changes made by commits in the current branch but that are not in are saved to a temporary area. This is the same set of commits that would be shown by git log ..HEAD. The current branch is reset to , or if the --onto option was supplied. This has the exact same effect as git reset --hard (or ).If is specified, git-rebase will perform an automatic git checkout before doing anything else. Otherwise it remains on the current branch. All changes made by commits in the current branch but that are not in are saved to a temporary area. This is the same set of commits that would be shown by git log ..HEAD. The current branch is reset to , or if the --onto option was supplied. This has the exact same effect as git reset --hard (or ).If is specified, git-rebase will perform an automatic git checkout before doing anything else. Otherwise it remains on the current branch. All changes made by commits in the current branch but that are not in are saved to a temporary area. This is the same set of commits that would be shown by git log ..HEAD. The current branch is reset to , or if the --onto option was supplied. This has the exact same effect as git reset --hard (or ).
  • by rustalot42684 (1055008) <(moc.tnuocca) (ta) (ekaf)> on Saturday June 02, 2007 @10:37PM (#19367775)
    We ALL know that the people who use CVS and SVN are version control Nazis!
    • Re: (Score:3, Funny)

      by Anonymous Coward
      Revisionists?
  • by RootsLINUX (854452) <rootslinux@NospAm.gmail.com> on Saturday June 02, 2007 @10:39PM (#19367781) Homepage
    I've used CVS, SVN, and GIT in serious projects and I can say I far prefer SVN to GIT, and GIT to CVS. GIT was incredibly confusing to use, and it may just have been the way the repository was administered was poor, but I never knew if I was synched with everyone else's checkouts and the command names made no sense. Its been over a year so I don't remember the details of GIT, but I remember having to do a lot of things "twice". Need to do a checkout? Two commands. Need to commit? Two commands. It was a bitch to use and I am glad I'm done with it. SVN, on the other hand, I felt very comfortable with from the start and most important of all, I trusted SVN to do what I wanted it to and to keep me from screwing up. In a year of using it, it has failed to lose my trust.

    I'm not trying to say SVN is better than GIT. The best repository depends on the type of project and type of development. But defaming SVN in favor of GIT is not, I believe, a valid statement. Especially when (I'm pretty certain) many, many more projects use SVN rather than choosing to use GIT.
    • by Black Acid (219707) on Saturday June 02, 2007 @11:57PM (#19368167)

      Its been over a year so I don't remember the details of GIT, but I remember having to do a lot of things "twice". Need to do a checkout? Two commands. Need to commit? Two commands. It was a bitch to use and I am glad I'm done with it. SVN, on the other hand, I felt very comfortable with from the start

      Most distributed version control systems exhibit this phenomena, because by "checking out" you are actually doing two operations: pulling the latest changes from someone else, and updating your workspace. For example, in Monotone you would type (I imagine git operates similarly):

      mtn pull
      mtn update


      The first command retrieves revisions from the server, and the second updates your workspace with those new changes. To "commit" a change, in a distributed version control system you first 1) commit the change to your local repository and then 2) push it to someone else:

      mtn commit
      mtn push


      It is often useful to keep these operations separate. For example, you can commit without pushing. Make a bunch of changes, commit each one separately, and only push once you're satisfied with the result. Other developers can still see each change you made individually, but only after you've pushed, so they won't be stuck with an incomplete in-progress version of the tree.

      Similarly, by being able to update without pulling, you can revert to any revision you would like without contacting the network. Likewise, since commit does not require network access, it is no extra effort to work offline. Once an Internet connection is available, you can synchronize your repositories, but in the meantime you can make any change you want - even with no network connection.

      The main disadvantage of a decentralized version control system is that it requires workflow changes [pidgin.im] to get the most out of it. If you are only familiar with centralized version control systems, it will take some time getting used to. But I'm glad to say, an increasing number of projects are making the change to distributed version control [slashdot.org], among them, Mozilla and Pidgin. They are not using Git (but Mercurial and Monotone, respectively) but they're all distributed. Git is being used by the Beryl [beryl-project.org] project, among others. Subversion has momentum in FOSS because it is familiar for those used to centralized version control (everyone knows CVS), and SourceForge [sourceforge.net] provides free SVN hosting. Once a free open source hosting site provides hosting for a distributed version control system, I expect more low-resource open source projects to use it.
    • I've not used GIT much myself, but I did watch the video. Linus pointed out that the UI has only recently stopped sucking. Since it's been over a year, it is definitely time for another look.
  • by suv4x4 (956391) on Saturday June 02, 2007 @10:41PM (#19367793)
    No one said that if you're famous and contributed something incredible to the world (such as Linux) you can't speak out of your ass most of the time, just because you enjoy how everybody listen and try to decipher if they should care about it, or just laugh and pass by.

    I use SVN if a medium sized team and see SVN used extensively in all kinds of projects around the globe with great success. I personally love the workflow of SVN.

    The only thing that they need to work is merging of branches, and incidentally I've talked to the developers, they're quite aware of this flaw of SVN and working on it. We'll see new versions that can track changes in each branch and even attempt automated merges with good success.

    I know a guy who has the same personality like Linus. The guy is very smart, he single-handedly is coding an application which is very popular in its area (won't mention it since that's internal stuff). He keeps bitching all the time: about customer feature request, about random products and how sucky they are, how people can't see that. And he could also change his opinion overnight for no apparent reason and go in the other extreme. But he's a friggin' programming genius and what he does is great, despite is takes a lot of effort to deal with him.

    Well, probably those two go together: being an amazing creator, and being an amazing ass with huge ego. Who knows.
    • by True Vox (841523) on Saturday June 02, 2007 @11:37PM (#19368083) Homepage
      Well, probably those two go together: being an amazing creator, and being an amazing ass with huge ego. Who knows.

      I disagree entirely that those two traits must go together. I'm living proof that you're wrong, in fact. I don't have a creative bone in my body.
    • Re: (Score:3, Interesting)

      by SnowZero (92219)

      I use SVN if a medium sized team and see SVN used extensively in all kinds of projects around the globe with great success. I personally love the workflow of SVN.

      If all you've ever known is centralized version control, you don't know what you are missing. Having used *both* centralized and decentralized version control on the same projects, I can say that decentralized wins hands down, but you have to work with it for a while to truly appreciate it.

      The only thing that they need to work is merging of branch

  • by paroneayea (642895) on Saturday June 02, 2007 @10:46PM (#19367815) Homepage
    ... And that is that CVS/SVN are centralized, while GIT is distributed, like GNU Arch.

    There are appropriate uses to both of these, and in kernel development I think it makes sense to have distributed development. However, in smaller projects, which really *need* a very specific direction (example, Wesnoth, I would think would not have gotten where it is today if there were so many branches where people were all making their own art).

    Linus is enough of a famed leader that he's going to be listened to, and thus kind of pulls the community around him as a central source of development. That's not necessarily going to happen everywhere.
    • Re: (Score:3, Informative)

      by koreth (409849) *
      Nothing about git prevents you from establishing a repository and telling all your developers that it's the central integration point for your project. It supports svn-style centralized development just fine. (In fact, it even interoperates bidirectionally with existing svn repositories, though you lose some of the advanced features.) The difference is it doesn't force you into a centralized model.
    • Re: (Score:3, Interesting)

      by grumbel (592662)
      ### However, in smaller projects, which really *need* a very specific direction

      Yes, but that isn't an argument why you should cripple your SCM. I absolutely agree that for a lot of projects there is little to no use for distributed repositories. However just because you don't need distributed repositories doesn't mean you can't take advantage of them, i.e. you get proper offline support and you get also a proper way to distribute changesets, which SVN still doesn't support (i.e. no "svn diff/patch" that act
  • "Subversion used to say, 'CVS done right.' With that slogan there is nowhere you can go. There is no way to do CVS right."

    Cvs is already done right. These would-be improvements are pointless.
    • by drgonzo59 (747139)
      Yes, that's your opinion and then there are hundreds of project and thousands of developers who disagree. If CVS was so good, there would not be an army of people behind SVN.
      • by jgrahn (181062)

        If CVS was so good, there would not be an army of people behind SVN.
        If CVS was so good, there would not be an army of people using MS SourceSafe ..?

        OK, CVS sucks. But it sucks in well-defined and well-known ways. That's enough for me and many others, for the things we do.

    • by abigor (540274)
      I can only assume you've never actually worked with it on a large project.
      • by fnj (64210)

        I can only assume you've never actually worked with it on a large project.

        You would be wrong. Any other assumptions based on nothing?
    • Cvs is already done right. These would-be improvements are pointless.

      I manage a 7 GB CVS repository serving 200 developers and you are totally wrong. If I could get buy-in from the 10 or 20 relevant stakeholders I would change to mercurial [selenic.com] in a pinch.

  • by Anonymous Coward on Saturday June 02, 2007 @11:01PM (#19367891)
    I took a look at git a while ago and was completely underwhelmed. The UI was so bad it was useless, and it didn't "seem" to do anything that Darcs didn't do. (I used to love Darcs because of the automatic patch dependency computations).

    Now that all the "next generation" SCM tools have matured somewhat, I took a look at all of them again. I had to stop using Darcs because of the "patch of death" problem, which basically is this: after using Darcs on a project with long-lived parallel branches, the repository may eventually enter a wedged state you can't get out of, due to exponentially complex patch dependencies. Oops.

    At this point I had an idea of what an SCM should do, how it should work, what the "mental model" should be. I want to create changesets, add them to branches, combine multiple branches (and keep track of renames and so forth between branches), re-order changesets, collapse multiple changesets into one, discard old branches, etc.

    Of course, CVS and close cousin Subversion are SO UTTERLY USELESS I didn't even consider them. Seriously, Subversion is like gold-plated shit. Looks nice but it's still shit. Reading people say stuff like "Subversion is awesome" makes me wince. How can something that doesn't have "real" branches, and doesn't have tags OF ANY KIND, be useful for anything? How do you keep track of multiple merges between branches? Answer: you don't. Or you keep track of revision numbers using svnmerge and pray it all works. Even the Subversion docs sortof hand-wave this away. I.e., they hand-wave away one of the FUNDAMENTAL ASPECTS of source code management: branching and merging. It's like hearing people talk about OO databases. They mean well but they just don't comprehend the generality of the underlying problem.

    That's why I was so excited about Darcs: the author "gets it". Unfortunately the implementation is flawed.

    I checked out a few more (Mercurial, bzr) but finally settled on git because it let me do all the things I needed to do, and it did them FAST. Once I figured out the underlying model I was pretty impressed. Git can be viewed at many levels: very low-level plumbing, or UI-level, or in between. The UI and documentation is still pretty shitty, but thankfully they are working on improving it and are moving away from the idea of having interchangeable UIs. Just focus on improving "core git".

    One great thing about git is that so much of it is just files in the .git dir and shell scripts that combine very simple low-level functions. For instance, you can create a branch just by saving the SHA1 ID of the tip into a file in .git. You can branch off any point in the history this way, including branches you've deleted in the past (git keeps all the old commit objects by default, even ones that aren't pointed to by any branch or tag.. this is very simple and understandable model, like reference-counting in a way).

    The other great thing about git is how easy it is to sling changes around and reorder them and combine them. For instance let's say you add a file to your project as commit "A". Then you add some code that uses this file as commit "B". Then you fix a bug in the file as commit "C". So you have A-B-C. Now you'd like to combine A and C into a single patch A', and put B on top of it, like this: A'-B. In git, this is super-easy. I can think of two ways to do it off the top of my head.

    I was checking into a CVS project the other day (for a client) and wanted to do this. Then I realized, you can't move things around in CVS like this *twitch*. So nowdays I do everything in git and only after the changes are beautiful and self-contained and well-commented do I check them into CVS one at a time.

    Okay so they point is, check out git (or honestly? Checkout out ANYTHING that isn't CVS or svn). Even if you think Linus is an asshole (which he is) or you don't like the git UI (it's not that bad now), check it out anyway.

    And if you don't use SCM at all? You suck. Start learning. It's a best practice that you can't live without, once you start.
    • by sqlrob (173498)
      WTF are you talking about? It's trivial to branch and merge in SVN.
      • Re: (Score:3, Interesting)

        by lorcha (464930)
        subversion lacks multiple merge points.

        Making a single branch and then a single merge is trivial in subversion. Doing anything more complicated is a nightmare.
    • You sound like a lisp coder, talking about all the features the competition doesn't have, but you can't live without. I don't mean that in a bad way, but the similarity is very striking. I guess right now GIT is the Lisp of SCMs. I hope it can catch on better, though.
    • Re: (Score:3, Informative)

      by vidarh (309115)
      Reading people say stuff like "Subversion is awesome" makes me wince. How can something that doesn't have "real" branches, and doesn't have tags OF ANY KIND, be useful for anything?

      The concept of tags is a crutch for systems where a versioned copy operation is too expensive. Since subversion keeps track of history across copies, and also doesn't copy the file content unless there's changes, there's simply no reason to have a separate concept of tags in subversion. The reason systems like CVS has tags is

  • by Black Acid (219707) on Saturday June 02, 2007 @11:24PM (#19368003)
    The ultimate reason why Linus dislikes SVN, CVS, etc. is that it is centralized. Everyone checks out source from a central server and commits their changes to the same centralized area. This has problems: your workspace is not versioned. By this I mean, you cannot track local changes to your workspace without committing them to the central server.

    A common pattern in development is to try one approach, test it, tweak it, and possibly try another approach if the first did not work out, perhaps reverting to a prior approach. With decentralized version control, you can commit your changes to a local repository and work from there. All the locally changes you make are versioned, and be committed, checked out, examined all without contacting a central repository. This is ideal, because you often want to try various options to find the one that works best, before pushing your changes to the rest of the world. In centralized version control, you can use a branch for this purpose, but often branches in these systems are difficult to either create, merge, or maintain, so they are rarely used. The end result is that with centralized version control, developers version their workspace in their head. DVCS systems remove the mental burden.

    Fortunately, FOSS developers are realizing the usefulness of DVCS and major projects are converting to some form of DVCS. Mozilla is switching to Mercurial [mozillazine.org]. The Pidgin [pidgin.im] project, which just released 2.0.1, is using Monotone [pidgin.im]. (Linus favorably mentioned both of these distributed version control systems in his Git talk, as they are both are distributed).

    Once you accept that DVCS is better than the centralized model (which may not be true for some situations), only a few (but growing number of) version control systems are viable. This is currently a hot area in open source development, with software such as GNU Arch, Monotone, Mercurial, Git, Darcs, Bazaar, and more paving the way. Many open source DVCS's are still in development and not ready for general usage. I can't speak for Mercurial, but Monotone doesn't have the greatest performance, instead preferring integrity over speed. This led Linus to write git, since speed is very crucial for a large project like the Linux kernel.

    Whatever the actual program (git, Mercuial, or Monotone), more and more open source developers are realizing the advantages that distributed version control can offer. I encourage all developers that haven't used any DVCS to try it -- once you do, you won't go back.
    • There's one trick to getting performance from monotone, which is to flip a switch on your workspace to make it use timestamps (like SVN does) instead of always re-hashing every file to see if it's different. For small projects, the rehash is best since it is certain. With timestamps on unix if you make changes in 1 sec, for example copying a different version right after a update (which can happen btw) then version control will not check in your changes and they can be lost.

      Once you enable timestamps with
      • by Black Acid (219707) on Sunday June 03, 2007 @01:45AM (#19368571)
        Monotone's inode prints [monotone.ca] (which, incidentially, Linus was a major contributor of [mail-archive.com]) can speed up some things, but the initial pull of a large repository is still unacceptably slow. The Pidgin developers have worked around [pidgin.im] this performance bottleneck by supplying bzip2'd Monotone databases via http, which the developer then can sync with the latest repository on pidgin.im to obtain an up-to-date database with the latest changes. Partial pulls should partially fix this problem in a future release of Monotone, or so I hear.

        For what it's worth, I use Monotone daily and find the performance acceptable. For the record, Linus used Monotone at a particularly bad time it its development cycle [mail-archive.com], when it was very slow and the main designer was on vacation. Nonetheless, the Monotone developers emphasize correctness and integrity over speed, and Mercurial and Git were direct responses to the performance of Monotone. Still, the performance of Monotone is always improving.
    • by A beautiful mind (821714) on Sunday June 03, 2007 @02:35AM (#19368773)
      Richard Dawkins spent a good deal of time in his book, "The Blind Watchmaker" talking about what the gradualist and the punctuationist view of Darwinism is. His gripe was that the latter was sold as a whole new theory, opposing the old gradualist view. Dawkins was rightly pissed about this, because the latter is merely an improved version of the former. I feel the same about the Centralized vs. Distributed topic. The distributed system is basically a centralized system where EVERY COPY HAS FULL REVISION HISTORY.

      There is still a central or main copy, otherwise you'd be herding a lot of slowly diverging forks! Most projects want to produce a release eventually and there is a main copy of sourcecode which the release is produced from.

      Imo, the reason Linus dislikes SVN and CVS and pretty much everything else is because of speed, because most SCMs lack the ability to work with merging different copies of repositories and work on a commit level instead, and do not allow for easy development routing around the central copy.
    • Re: (Score:3, Insightful)

      by putaro (235078)
      What you're citing as advantages for decentralized version control are not the result of decentralization.

      Cheap branches? Subversion has cheap branches.
      Better merging? This is a result of algorithms has nothing to do with whether the system is centralized or not.

      If you're on a fast net with the server you can commit as often as you like. If you can branch/merge easily it's no problem.

      If you want to cite advantages for decentralized version control it might be more like:

      If you have to talk to a server ove
  • by Excelcia (906188) <kfitzner@excelcia.ca> on Saturday June 02, 2007 @11:29PM (#19368027) Homepage Journal
    Linus talks about his distributed model, how everyone has a branch, and how this avoids politics associated with who gets commit access. He claims (and I admit I've seen this happen in some) that many projects have quite the internal politicking on who has CVS commit access. But then he claims that Git's special sauce eliminates these internal politics. Ok, I was intrigued, so I listened on.

    Essentially, he explains, the secret with Git is that everyone has commit access on their own branch - they do whatever they want. He says that the way it works is that someone does something cool with their own branch, then they start hollering to say "Hey, I have a good branch, merge mine" and it will get merged. Politics over.

    Ok, so now I'm scratching my head. How is this a fundamentally different paradigm? In CVS, basically anyone can check out the whole tree and make any changes the like. They can then say, see, my changes are good and ask for them to get committed or ask for commit access themself. In Git, this commit access bottleneck is just moved from the commit stage to the merge stage. You make your changes, commit them to your separate and unique branch, and then ask someone with to merge it, or give you the ability to merge it in to mainstream. How exactly does this eliminate the politics? You are still going to have some people with "the power" and some people without. In any project where you have people who are going to fight about who gets commit access, you'll just have a fight about who has the ability to merge into mainstream.

    So, ok, distributed is nice (though for some projects central may be preferred) but I don't see how this magic system bypasses politics. In fact, I can potentially see more internal politics over this method. I can see factions gathering to support this or that branch, arguing about which is better, fighting about which one gets merged in. I can see the potential for branches going longer between merges, and more changes happening at once, making it harder to track problems. I don't claim these scenarios are more likely, but I do claim that this changing from a commit access to a merge access paradigm is just renaming the problem.

    • You may be saying this in the context of large FOSS projects, but for most projects, not allowing all the team members to commit changes seems like a really bad idea. If you don't trust them, why are they on your team?

      Complaining about the occasional inefficiencies of file locking while forcing some developers to waste time waiting for permission to commit, seems really ironic to me.
    • Re: (Score:3, Interesting)

      by starseeker (141897)
      I tend to agree - what becomes the "official" code (i.e. what would go into a release tarball) is a social problem without technical solution. A coordinated release requires AGREEMENT, however that agreement is arrived at.

      What GIT does differently, as I understand it, is it makes flipping around branches much easier than before. CVS and SVN have the concept of a central server, so if two developers are trying to resolve differences in their branches before either can get their changes into the main tree t
      • GIT is a neat tool, and I think it has a lot of potential. But like every other technological solution, it does not and cannot resolve fundamentally social issues.

        On the other hand, it does allow for the web of trust / tree of merges solution that is impossible with a centralized SCM tool.

    • Re: (Score:3, Informative)

      by c (8461)
      > In any project where you have people who are going to fight about who gets commit
      > access, you'll just have a fight about who has the ability to merge into mainstream.

      I really wish he would have addressed that question a little more directly, too.

      I think the problem is that you're thinking about it from a classic centralized development model. I have some trouble getting my head around it, too.

      Basically, from a truly distributed SCM perspective, there is no "mainstream". All branches are equal. Obvi
    • Re: (Score:2, Interesting)

      by Endymion (12816)
      It is moving the problems to a neighboring problem-space, but that allows for a good benefit: getting everybody to check trivial changes in.

      (at least, that's what I got from his talk)

      I know I've seen it before - the problem where commits are restricted by management (for good reason), and people cannot commit their current work. I've seen this destroy some work before, as it means everybody is basically always running with a 1-2 week window of changes that are not checked in to the "safe, backed up". Ouch.

      I
    • by norton_I (64015)
      I think the way it is supposed to work (no idea how well it does for the linux kernel) is that anybody can "join" the development tree, publish "their" kernel version, including whichever patches they want, without interfereing with each other. Everybody has merge privileges on their own tree, and nobody has merge privileges on someone else's. The only reason Linus is "special" is that when he says "this is version 2.6.22, no bloody -mm -ac or -aa" everybody else listens.

      Ideally, such a system would blur
    • Re: (Score:3, Informative)

      by Error27 (100234)
      There are a couple things.

      Everyone has a complete tree so everyone can push patches between themselves. Linus doesn't have to accept it into his own tree. That cuts down on the politics. Before everyone had they're own tar ball and push patches around but you lose history and it takes more work.

      The other thing is that it's easier to delegate political questions. Lets say Linus pulls networking patches without even looking at them. The networking maintainer gets to deal with all the political issues. T
    • by iabervon (1971) on Sunday June 03, 2007 @02:08AM (#19368641) Homepage Journal
      The advantage is that MergePrivileges can be fine-grained: there can be many answers for "merge into what?" There's a -mm tree, a -stable tree, a -linus tree, a -rt tree, and a lot of vendor and distro trees. Each of these has a different maintainer, and can have a different idea of what is acceptable. And only the maintainer can merge things into their tree, and they can decide based on a variety of features of the things they're considering. For example, Linus only merges from a few people directly: maintainers of various subsystems. And he doesn't even trust them completely; if the SD/MMC maintainer has a change which changes x86 architecture code in the tree Linus is asked to merge, he'll notice and ask what's up with that. And if there are changes that look too intrusive for the current point in the development cycle, he'll put it off until the next cycle, and ask for a tree with just fixes. And -linus isn't special, except that almost everybody trusts him implicitly and merges his stuff into their trees (the main exception being -stable, which is why a new 2.6.20.x kernel isn't derived from 2.6.21; and vendor and distro kernels are generally based on -stable of some sort, and only get new stuff from Linus when they go to a new series). Also, maintainers of subsystems know the people who work in their areas, and can apply the same sorts of rules: the guy from Intel who works on their network drivers can get e100 changes into the the -netdev tree, because the maintainer knows they know what they're doing for e100 changes. And Linus sees that the e100 changes are coming in through -netdev, and the network maintainer knows what policy to apply to the drivers around there, so they're fine, even if Linus has no clue who should be allowed to do what in e100.

      It's not that the politics go away. It's that the policy is no longer a binary "yes or no" decision, so the technical arrangement mirrors the social arrangement. This doesn't work with CommitAccess because people wouldn't commit the same change everywhere they should, and they couldn't be restricted to only making changes they're trusted to make (there are people who are trusted to correct spelling in comments in any file in the tree, and Linus can look through the total changes they send and verify that they only change spelling in comments).
  • by ClosedSource (238333) on Saturday June 02, 2007 @11:29PM (#19368029)
    If you have a project that has thousands of developers all of the world like Linux does, a SCM system that is focused on merging makes a lot of sense. Unfortunately, there is a tendency for some people to overdo merging on small projects when they don't really need to. If the application is designed in a modular fashion and developers are assigned specific modules, than merging is rarely needed. Of course, many control freaks don't like this approach because it makes it harder for them to "correct" other developer's code.
  • Every developer has their own repository, which they can commit as branches into a repository of repositories :P
  • by sohp (22984) <snewton@NosPam.io.com> on Sunday June 03, 2007 @12:42AM (#19368321) Homepage
    Distributed version control the way git does it (conceptually, not necessarily the implementation) is the best idea in SCM since concurrent development and optimistic merge conflict resolution on check-in.

    Notice how, even years after better ideas superceded the lock-modify-unlock paradigm, many tools and shops still use exclusive-lock SCM.

    It could be quite a while before you see anything like the way git does SCM in use in the majority of programming shops.
  • Actual Youtube link (Score:5, Informative)

    by beegle (9689) on Sunday June 03, 2007 @07:10AM (#19369907) Homepage
    http://www.youtube.com/watch?v=4XpnKHJAok8 [youtube.com]

    This is the video from the article. You can either watch it in the tiny embedded window, or you can go to youtube and click the button to watch it full-screen.

    Look, posters: if you're going to point to a video that's hosted on YouTube (or another video hosting site), just link to that site. Don't link to some random web page that has the video embedded in it.
  • SVN etc. (Score:3, Interesting)

    by Tom (822) on Sunday June 03, 2007 @03:22PM (#19373281) Homepage Journal
    He's right about CVS, and more or less about SVN. Except for one thing: Subversion works. Not only in the technical sense, but in the sense that you can work with it, you can easily explain it to new developers, there is integration into lots of IDEs, code editors and other tools and the list goes on and on. (last, but not least: Trac!).

    I used to be passionate about arch, for example. I'm fairly sure I would've been about GIT had it existed back then. But then I learned that to get real work done in the real world, the theoretical basis of your version control system matters little. If the system doesn't work for my developers - who like many projects are doing this for their fun and in their spare time - then it doesn't work, period. If I can't explain it to the boss at work, it won't get installed.

    And that's why Subversion is everywhere and arch is, where exactly?

    Now Linus is a man with his feet on the earth, so GIT may have a different fate. Wake me when Eclipse and Textmate have built-in GIT support and at least half of my potential developers know it.
  • by SpaghettiPattern (609814) on Monday June 04, 2007 @02:01AM (#19377919)
    I watched the video and was baffled by Linus' attitude.

    The guy is bright on technology but what he calls strong opinions I -and almost any business person- should call them shortsighted opinions that do not appreciate other people's way of doing things.

    Saying stuff like "Those of you that like SVN would probably want to leave the room. Because it's crap too." is very stupid. I for one like SVN. It's good enough for my purposes and it sure beats quite a few commercial tools I've seen. But I sure want to know hear Linus' thoughts on the topic. Mainly because different ideas keep my mind fresh.

/earth: file system full.

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