Linus says of the Github platform -

That's partly because of how the kernel is developed, but part of it was that the GitHub interfaces were actively encouraging bad behavior. Commits done on GitHub had bad commit messages etc, because the web interfaces at GitHub were actively encouraging bad behavior. They did fix some of that, so it probably works better, but it will never be appropriate for something like the Linux kernel.

I haven't ever looked at the kernel workflow, nor have I ever heard systematic criticism of Github's methodology. Does anyone else have input on what Linus may mean by his opinion?

The kernel development model is documented here: http://lxr.free-electrons.com/source/Documentation/developme...

Github doesn't scale at all for large projects. The kernel is averaging over 8 changes an hour, 24 hours a day. That rate of change can never be handled by doing pull requests and web site review. It only can work with email and review and scriptable processes.

Eh, I mildly disagree on web site review. Perhaps not GitHub's pull request/review model, but big projects like Android and Chromium do all their review on web interfaces.

Using Gerrit, which is an automated mimick of Linus' development model.

By the way, we've been succesfully using Gerrit on smaller-scale projects as well (around 8 change-requests / day) and don't even want to think about going back to pull-requests.

But don't "trusted lieutenants" (yourself included?) mitigate a lot of the challenge posed by that high rate of change?

    > [...] nor have I ever heard systematic criticism of Github's methodology.

He's not only criticizing Github:

    > (a) make a real pull request, not the braindamaged crap that github
    >     does when you ask it to request a pull: real explanation, proper email
    >     addresses, proper shortlog, and proper diffstat.
    >
    > (b) since github identities are random, I expect the pull request to
    >     be a signed tag, so that I can verify the identity of the person in
    >     question.

Real explanation, proper shortlog, signed commit, etc. (Note that he didn't mention emojis.)

All he seems to be asking for is that we take our time and do it properly. Makes all the sense in the world for a large, long-lived open source project like Linux. Imagine 20-year-old commit messages from FreeBSD would look like the ones we write today for, say, a npm module.

--- edit ---

Yeah ... nevermind. He explains it himself further down:

    > Btw, Joseph, you're a quality example of why I detest the github
    > interface. For some reason, github has attracted people who have zero
    > taste, don't care about commit logs, and can't be bothered.
    >
    > The fact that I have higher standards then makes people like you make
    > snarky comments, thinking that you are cool.
    >
    > You're a moron.
    >
    >                 Linus

"You're a moron."

That's our Linus-kun.

Also who's the "Joseph" he's addressing? Unless there are deleted comments, the only snark is coming from a dude named Jaseem.

I was so happy to read this. I completely agree with Linus' criticisms of the pull request system that GitHub has popularized. They've deeply embedded really bad habits into programmers. I used to wonder "Why do some projects still do patch review on a mailing list?" and then I realized it was for the reasons that Linus gave here.

Let's not forget the other contender for replacing Bitkeeper, Mercurial:

http://lkml.iu.edu/hypermail/linux/kernel/0504.2/0670.html

We will also be celebrating Mercurial's 10th anniversary next week during the 3.4 Pycon sprint:

http://mercurial.selenic.com/wiki/3.4sprint

I used Git for a couple of years then changed to Mercurial and have never looked back, except now and then to wonder at the size of the crowd that has gathered around Git, driven in no small part by the success of github (which is not a bad thing!)

Git is an entirely appropriate tool for managing as something as large and complex as the Linux kernel, but I'm doing much simpler stuff, and Mercurial is simpler and has a much shallower learning curve. I'd recommend it unequivocally to teams of modest size working on average applications.

The state of git documentation is much better today than it was five or six years ago, so maybe its complexity is less of a big deal, but so far I've not encountered any issues with Mercurial that make me think "If only I was using git this would be easy!"

What I found with git was I had to maintain a fairly complex mental model of the current state of affairs, and because I'm not very intelligent that took quite a bit of effort. With Mercurial the model is much simpler, so I can spend more of my very limited attention on writing code. It's quite possible that I simply never took the time to learn git properly, but with Mercurial I didn't have to.

I won't comment on Mercurial because I don't know anything about it.

I really do feel like Git is appropriate for small projects. The .git store is incredibly small (because it only stores changes) and quite simple when you get used to it. You will only only need to use a tiny subset of Git's functionality (or, heck, just the Github web-UI if you wish).

I think the hardest thing about Git for big and small teams is getting used to the mental model of Git (branching, merging, master, etc). Once you get it down you realise that Git is less complex, not more...

PS - This comment is mostly in reply to the implication that Git is a better tool for large and complex projects like the Linux Kernel.

PPS - Mercurial might be a better tool yet still for small projects, I don't know enough about Mercurial to have a qualified opinion either way.

For all intent and purpose, git and hg are fairly equivalent. In day to day usage, the two big differences are:

1. Local branches

Git has them, mercurial doesn't really. Mercurial wants you to use a lightweight clone (copy-on-write with hard links) instead. Lots of mercurial extensions deal with this however.

The lack of rebase in stock hg is probably directly driven by the lack of local branches that don't get pushed upstream by default.

2. Committing code

Mercurial, without extensions, doesn't have the git shelf. With extensions there's a few competing options like MQ, Shelve or Evolve.

Both these points make hg easier to learn (branch == clone is very easy to wrap your head around, commit behaves basically like svn/cvs).

For several years now Mercurial has had bookmarks in core, which are analogous to git's local branches.

It's also worth pointing out that many of the extensions you referred to (rebase, shelve) are bundled with core Mercurial and need only a one-line addition to a configuration file to turn them on. Extensions bundled with core Mercurial have the same level support and backward compatibility guarantees as the rest of Mercurial. Part of Mercurial's command line philosophy is to not include obvious foot-guns (like the ability to rewrite history) in the default version.

And for several years bookmarks have been unfortunately missing in unfortunately common linux distributions.

Mercurial wants you to use a lightweight clone....

You can make a named branch and make it private so that it wont be pushed automatically or you can create a bookmark and mark the changeset as private, so that it wont get pushed automatically OR you can create a local clone, completely isolated from the origin repo.

The difference between git branches and Mercurial branches is a bit of a conceptual one. Git has 'user' branches, where a branch corresponds to the work of a user. Mercurial has 'feature' branches, where each named branch (is supposed to) correspond to a feature. I think This is the one of the reasons some Git users are sometimes so turned off when they see Mercurial branching model. And to me, I would like a project as a sum of its feature branches. But I can imagine why this might not be optimal for a something like Linux kernel. But for most projects, I think feature branches are more valuable than the user branchs of git.

Mercurial, without extensions, doesn't have the git shelf.

Shelve extension is bundled, enabling is just a matter of turning on a flag in the .hgrc configuration file...

Git has 'user' branches, where a branch corresponds to the work of a user.

Er. Not really, no. Git is simply agnostic about how you use branches, and allows you to separate how published branches and your local branches are used implicitly. I've rarely worked on a multi-user git project where published branches corresponded to a user's work. Almost always they are feature branches worked on alone or with someone else.

Even in linux development, where the repositories are directly tied to users usually, the actual branches generally represent a work-unit of some sort, so I'm not sure where you got this idea.

It's probably pervasive because of github and pull requests where, at least for open-source projects and external contributors, it's true in practice though not enforced.

This is where I got the idea,

http://fossil-scm.org/xfer/doc/trunk/www/fossil-v-git.wiki

Please see the Table on the top and the 'Branches' section.

1. Local branches

Local branches are really an artifact of Git having a garbage collector. That means that any commit that you want to keep must be attached to a branch so that it may not be inadvertently lost. Without a garbage collector, that is not necessary.

In particular, in many other VCSs, you just simply commit without having to create a branch in the first place. Labeling them (via whichever mechanisms your VCS provides) is typically optional with modern version control systems.

You can argue that you prefer having a garbage collector over having to explicitly delete commits/branches that you do not want any longer, but that would be a different issue.

2. Mercurial, without extensions, doesn't have the git shelf.

This is sort of incorrect -- or rather, probably a misunderstanding. Shelve is part of standard Mercurial and has been for a while (same goes for MQ). While it is disabled by default and enabled in the extensions section, it's no more an extension in any meaningful sense of the word than git stash (which technically calls out to a shell script [1]). Mercurial's shelf is a python module [2] that is loaded when you flip a switch.

Both these points make hg easier to learn (branch == clone is very easy to wrap your head around, commit behaves basically like svn/cvs).

This is really more a feature of Bazaar, not Mercurial.

[1] https://github.com/git/git/blob/master/git-stash.sh

[2] http://selenic.com/repo/hg-stable/file/default/hgext/shelve....

In particular, in many other VCSs, you just simply commit without having to create a branch in the first place. Labeling them (via whichever mechanisms your VCS provides) is typically optional with modern version control systems.

Since, for me, local branches are a massive part of why I prefer git, I'd be interested in examples of how to do the same thing in other VCSs.

It doesn't make sense to me that they're a byproduct of having a garbage collector, since (1) git-stash exists, (2) local branches are a common selling point, and (3) git-clean honestly seems tacked on rather than a core piece of the design.

For Mercurial, you create a new local branch by committing at a point that's not a tip (or not HEAD, if there's just a single branch).

By default, it doesn't have a special name (like a git branch does). You can give it a name via "hg bookmark".

The feature set is honestly fairly similar, it's just different in the way it is presented. In git you go into a "detached HEAD" and have to explicitly name a branch or commits will get lost. In hg you commit and it creates a new tip, but it doesn't have a name unless you explicitly name it via bookmark.

In git you go into a "detached HEAD" and have to explicitly name a branch or commits will get lost.

Maybe I'm missing something, but this seems like a fairly academical scenario.

When would you checkout a specific commit, keep working, keep committing, but not attach it to a name or a branch? How is "67846237864237846" a nicer reference than "bugfix" or whatever?

To me this seems like people using git in a way it's specifically designed not to support and then go complaining when things go wrong.

Since, for me, local branches are a massive part of why I prefer git, I'd be interested in examples of how to do the same thing in other VCSs.

You simply commit a new changeset based on the desired parent. The branch would be created implicitly by having a revision with two or more children. It does not have to carry a name; naming revisions (or sets of revisions) is an orthogonal concept for the purpose of navigating the revision DAG [1], whereas in Git branches have the additional purpose of keeping revisions from being GCed. Any revision that is not referenced by a ref (directly or indirectly) will eventually be GCed (once it is removed from the reflog and the grace period has expired).

It doesn't make sense to me that they're a byproduct of having a garbage collector

It is a byproduct. Because if you did the above in Git (which Git won't let you without being explicit about it, but it's possible), then one or the other child would get GCed sooner or later. That's because there's only one HEAD commit, and that can prevent only one child from being GCed, so you have to create a ref to the other (generally via a branch) to keep it alive.

since (1) git-stash exists [...] and (3) git-clean honestly seems tacked on rather than a core piece of the design.

This has nothing to do with git stash or git clean. I'm talking about one of Git's architectural principles, where the repository is essentially a purely [2] functional data structure and revisions that are not reachable from one of the roots (refs/branches) are subject to garbage collection.

[1] And if you look (aside from Mercurial) at Bazaar, Fossil, Monotone, or Veracity, you'll find that there are multiple ways to go about that.

[2] Well, not entirely pure, but close enough.

whereas in Git branches have the additional purpose of keeping revisions from being GCed..

Not only that, but it is also used to decide what all commits to show to the user. In that way branch names act as little windows through which you can look at the DAG of history. Commits that you cannot see through this window does not really belong in the history according to git, and will be GC'ed.

So if you make a commit on top of a revision that is not a branch head, then it becomes a DETACHED HEAD. Actually there is nothing 'detached' about it. It is linked to the parent commit just fine. But git just does not consider it part of the history unless you give it a name. Here you can see the problem with git naming. 'DETACHED HEAD'. If you understand a head revision as a last revision in a sequence of connected commits, how can there be a 'DETACHED HEAD' when a 'HEAD', by definition is part of a sequence of commits..

I wonder why someone would call it a 'DETACHED HEAD' instead of something like 'UNNAMED HEAD' or 'ANONYMOUS HEAD'....

You simply commit a new changeset based on the desired parent. The branch would be created implicitly by having a revision with two or more children.

And then, how do you later track these commits? How do you change or merge branches if they have no names? Do you go around remembering revision-IDs?

I'm not trying to be judgemental and say this is wrong or anything, but I'm curious how this works out in practice.

    > The .git store is incredibly small (because it only
    > stores changes)

git stores a complete copy of each revision, not changesets. (Well, it is my understanding that a .pack compressed archive of objects may store some of the objects as changesets, but that's not the general case)

It stores a complete copy of the file, not a complete copy of the entire repository. So it keeps your .git fairly light weight since only changed files have duplicate copies.

Essentially it is not line level, but file level, rather than complete repository level (e.g. like Team Foundation is).

So it keeps your .git fairly light weight (... compared to ...) Team Foundation

And you can tell from how the product is being used. Where I work, we use TFS and you literally need to have committee meetings before a new branch is made.

You need to agree on long term strategies, you need to agree on branch hierarchy (because TFS cannot merge without one), you need to replicate all-the-things(tm) for your new branch, you need to adjust your versioning-strategy for this branch, and possibly future branches which may come and may not ever collide with this one, because TFS branches are massive and carved in stone. They are forever. Etc etc.

You never branch more than once a year. In the world of TFS, doing such would be madness, haphazard. Or at least you would need a full team doing nothing but branching and merging and integration. And good luck trying to find qualified people willing to have that as their day-job.

With git you branch every single time it makes sense, usually several times a day. And your life is nicer because of it.

It's funny how such technical decisions results in such huge and enormous visible changes to how a product is being used.

Somewhere deep in Microsoft there are probably one or more engineers crying right now seeing the effects of their (back then) seemingly innocent decision, as they themselves are forced to deal with TFS in their daily work and they see how nice the gitters have it.

Internally Microsoft largely uses a fork of Perforce called SourceDepot. Branching in P4 is about as easy and lightweight as any centralized version control system has ever managed, though still quite a bit heavier than git obviously.

When I worked in Google a couple years ago, they were using Perforce and branching was extremely hard (it was P4 with extensive internal tooling around/underneath it, no idea how representative it was of normal P4).

It took me about a year to realize how bad it really is: eventually I found my way to a "how to create a dev branch" document starting with:

    "Last year Dev Wossname wrote a useful mail showing how to create a dev branch and got most of the details right :-)  This howto explains it in more detail and fixes a few points."
    Then followed a quite few pages with a dozen manual actions doing somewhat intimate things to levels of P4 I had not previously heard of...
    Oh, and it created the branch at the *company-wide root level*, e.g. `gmail/` -> `gmail_dev_branch_2012/`.  No pressure !-)

It then took a few more days until the horror of that opening sentence sunk in. Native large-scale branching was so rare that it was almost a lost art!

[There were also several "lightweight" branch-like techniques based on symlink magic, FUSE filesystems and more magic. Those were routinely used for freezing a release build, with option to hot-patch it — but IIRC it was impossible to merge back onto the main tree.]

In practice things weren't that bad because (A) Google got really good flow (especially continuous testing) for everybody working close to HEAD, (B) personal branches were easy and common:

- Fresh checkout directories were cheap [should have been frightfully expensive but clever scripts and a FUSE filesystem fixed that]. - Every CL (commit progressing through code review iterations) was effectively a feature branch. - People who wanted more used a somewhat crazy, but very workable, internal tool mirroring a growable {time,space} subset of P4 into local a git repo and back onto P4.

Mercurial is not only simpler, but also has got really powerful features like revsets.

http://www.selenic.com/hg/help/revsets

I have tried to switch to git multiple times. Every time, I keep coming back to Mercurial. The most difficulty I have with git is the non nonsensical naming of concepts. For eg, A branch is a pointer to a commit. Because of this, I experience a big mental block when I try to reason about something. With Mercurial this is very much easier. And if you are using a DVCS to any capacity you ll have to do this often.

Another great thing about Mercurial is how easy to get help about stuff. You can head to the IRC chat room and can have a very good chance of catching one of the developers who, in my experience, were very helpful...

The most difficulty I have with git is the non nonsensical naming of concepts. For eg, A branch is a pointer to a commit.

This is a frustrating thing about how people tend to talk negatively about git. I think what you mean is "not named in a way I'm used to," because there's nothing nonsensical about this naming at all, and it's actually an incredibly simple and lightweight way to reason about naming things in version control (imo, I suppose). And it permeates basically every level of how git organizes information in a pretty darn uniform way.

To me mercurial's two kinds of built-in branches and several plugins to do branch-like things is much more complex, but I still wouldn't call it nonsensical. That'd just be admitting that I stopped thinking about it when it was strange and unfamiliar to me.

I think what you mean is "not named in a way I'm used to,"..

Of course, that is the whole point of naming something sensibility..Just, for example, imagine how hard it would be if you have to learn/work in a version of C that calls pointers as 'branches'.

To me Mercurial's two kinds of built-in branches and several plugins to do branch-like things is much more complex, but I still wouldn't call it nonsensical.

I don't know what you mean by 'several plugins to do branch like things'. Isn't it more frustrating that people complain about a tool because they have to enable some advanced stuff by configuration. But I agree that Mercurial is actually complex than Git, because it provides more options to the user. So the complexity of Mercurial is a side effect of it being more powerful IMHO.

So the point is I say, naming a 'pointer to a commit' as branch, is nonsensical because it goes against our notion of the word 'Branch' from real life. It adds unnecessary burden for a human being trying to think in the language of the tool, without actually making the tool more powerful. Git could have been as powerful as it is now even if it had named things better, Right?

Of course, that is the whole point of naming something sensibility..Just, for example, imagine how hard it would be if you have to learn/work in a version of C that calls pointers as 'branches'.

Yes, if you rename <arbitrary thing> to <other arbitrary thing>, it is very likely to result in nonsense. This is not such a case.

A branch in git is literally a name for a branch of the DAG that is the commit tree. It's possibly the least abstract interpretation of the concept as possible. There is nothing nonsensical about it.

But the objection seems to be that you don't work with it like in svn or hg or p4 or cvs (which are also all different from each other), which does not make it nonsensical, merely unfamiliar. This is the distinction I'm driving at.

But the objection seems to be that you don't work with it..

The objection is that, when naming is skewed in lower levels it makes it harder to reason about higher level concepts and creates ambiguity..

For example, let us continue with the idea of a 'branch'...

Suppose you define a branch as 'a set of commits'. Then it is easy to imagine a 'remove' operation on a 'branch' will remove all the commits in that 'branch'. There is no ambiguity.

But when you define a branch as 'a pointer to the last commit in a consecutive set of commits', a 'remove' operation on a branch is no longer clear what it is supposed to do.

Does it simply deletes the pointer, in which case the commits will remain untouched? But it would not be consistent with the abstraction of the 'branch'.

Does it remove all the child commits from the history? by which the operation would be consistent with the abstraction of a 'branch'.

Now the remove operation is ambiguous as to what it actually does.

Note that there would be no ambiguity if the user does not know that a branch is actually a pointer to a commit. Because git hides all the change-sets that are not the decedents of a branch. So a users concept of a 'branch removal' is maintained. But I think it is pretty accepted that using git requires that you know stuff like these...

So another way of looking at the problem is that, Git forces the user to work at multiple levels of abstraction simultaneously. And this creates ambiguity because the user wouldn't know which level of abstraction to use when reasoning about something, and defeats the whole point of having abstractions in the first place IMHO.

Then it is easy to imagine a 'remove' operation on a 'branch' will remove all the commits in that 'branch'. There is no ambiguity.

The problem is not with Git's use of pointers, but with your own thinking.

One should not be able to "remove" commits, because any operation should be undo-able. In git removing commits implies updating a pointer. And if those commits end up not being referenced by anything else, then they'll get garbage collected. What git does is very close to how persistent data-structures work. And many people complain about it just because it's unfamiliar.

And in your example, of course there's ambiguity, how can it not be? What happens with the branches that are forked from your branch? That's the definition of ambiguity right there.

So another way of looking at the problem is that, Git forces the user to work at multiple levels of abstraction simultaneously.

In my experience, the problem with Git is that people don't bother to read documentation for a tool that they are using every day.

I think we all understand why git branches are called branches, the problem is that it's a misleading name.

Git branches are pointers to commits. For example I can move the pointer to a commit to point to the previous commit instead. But the commit which was previously being pointed to is still there. However when I say that I reset a branch to a previous commit, I get the feeling that the branch was "cut", and so that the commit was lost - which is not the case.

This is why using the name "bookmark" is better in my opinion. Not because I'm used to it (I've used git much more than mercurial), but because it's a better representation of what is actually happening.

I don't know what you mean by 'several plugins to do branch like things'.

Maybe his knowledge of Mercurial is 5+ years old. In versions before 1.8 (2010 and before), bookmarks was an extension ("module") and you had to add a line in .hgrc to take it into use.

No, bookmarks were one of the two built-in versions I was referring to. I'm referring to things like this: http://mercurial.selenic.com/wiki/MqExtension

For eg

FYI, "e.g." stands for "exempli gratia" which is Latin for "For the sake of example".

So "for eg" is actually "for for the sake of example".

[1] http://en.wiktionary.org/wiki/e.g.

I moved from the other way from Mercurial to Git a while back.

I started using Mercurial because the basic interface and operations appeared more natural to me. Also, at least at the time, the Windows support was better in Mercurial.

After working with some repos using Git, I fell in love with the staging area, and the ability to selectively stage parts of files. I am sure Mercurial has something similar, but it was built into Git.

The only thing that bugs me is that the Windows port appears to be stuck at 1.9.5 (yes, I know it's open-source so I should go fix it instead of complaining).

The only thing that bugs me is that the Windows port appears to be stuck at 1.9.5

What? What gave you that impression? That's a really old version. Here's the last 3.3 Windows build:

http://bitbucket.org/tortoisehg/files/downloads/tortoisehg-3...

This was from the downloads page:

http://mercurial.selenic.com/downloads

Edit: Oh, crap, I completely misread that. You were talking about the git Windows version. Oh well. Mercurial Windows versions are staying quite up-to-date, thanks to the tireless work of Steve Borho.

Yes! Partial staging of files is amazing and I miss it sorely when I use hg. There must be a way to do it.

Use crecord. We're working on moving it into core:

https://bitbucket.org/edgimar/crecord/overview

If you want a "staging area" just use a temporary commit and keep ammending it with `hg crecord --amend`. There really is no difference between a commit and a staging area except the name. If you're afraid of pushing your WIP commit, use `hg crecord --secret` or `hg commit --secret` so that your commit will be in the secret phase and won't be pushed until you declare it draft with `hg phase --draft`.

Here is the first Git commit he talks about in the article:

https://github.com/git/git/tree/e83c5163316f89bfbde7d9ab23ca...

"The trick wasn't really so much the coding but coming up with how it organizes the data."

I think this really is the key to understanding git as well. When you understand the git data structures, git makes sense. Otherwise, it can be quite difficult to grasp (http://ftp.newartisans.com/pub/git.from.bottom.up.pdf was really useful for me).

Not only git. There is a nice quote from Fred Brooks Jr. (I think), that if you show me your flow charts and algorithms, I remain as clueless as before, but show me your data structures, and everything else will follow. (I am paraphrasing this from memory, Brooks put it more eloquently.)

Yes! I love that quote - so true. Linus has the same opinion:

"Bad programmers worry about the code. Good programmers worry about data structures and their relationships." [1]

I actually refered to this when discussing switching from Java to Python. One of the biggest problems for me was not easily being able to see the types of the arguments to a function in Python. [2]

[1] http://programmers.stackexchange.com/questions/163185/torval...

[2] http://henrikwarne.com/2014/06/22/switching-from-java-to-pyt...

not easily being able to see the types of the arguments to a function in Python. [2]

That's because of Duck Typing [1]. I really like Python for how quick and easy it is to make small pieces of software, but I fully agree that Duck Typing can become more of a hindrance on larger projects.

[1] http://en.wikipedia.org/wiki/Duck_typing

Nothing about duck typing requires a python-like type system. F# has duck typing via inlining (hacky sorta), C# has it too, but only for compiler use, not end user code (because why build generic features, when you can hack one-offs into the compiler).

It'd be great to have more static duck typing. I suppose that's the point of traits and mixins, to some extent. But it'd be nice to have on-the-fly constraints created and enforced.

I thought that F# used type-inferencing? If not, then its not nearly as similar to Haskell and OCaml as I've been led to believe.

Unless you're referring to type-inferencing when you use the term static duck-typing. The term duck-typing was never meant to refer to type-inferencing - duck-typing is type-opacity right into the runtime. The whole point of duck-typing is that objects can be referred to generically even in cases where their underlying type would be undecidable.

Type-inferencing gives you some of the source-level flexibility of not having to refer directly to an object's type much like duck-typing, but without many of the crazy runtime disasters that you can get with duck-typing.

C# Actually does have duck typing via the DLR (Dynamic Language Runtime) now. You can totally define a method as

    public dynamic DoDynamicStuff(dynamic wooDynamix)
    {
        Console.WriteLine(wooDynamix.DynamicProperty1);
    }

Off topic from the article, but this is something I literally just spent my morning wrestling with and fixing, so I'd like to talk/rant about it a little. My apologies in advance for rambling.

You can use doc comments to signify types. You mention you use PyCharm in your article, and it supports doc comments in it's autocomplete and code analysis, I find most popular libraries are commented well enough that PyCharm can understand them.

I also always try (and encourage others) to use names that are declarative for both purpose and type. Of course, you can't always rely on third party libraries (or even colleagues) to be so nice, but I find a good name (almost) always removes all the confusion that normally comes from a lack of static typing.

For example, one of Codecademy's very first Python lessons includes some code like this:

    meal = 44.50
    tax = 0.0675
    tip = 0.15

Which I think is unclear. Imagine these were function arguments. calc_total(meal, tax, tip) is vague. Is meal an object, or a numeric value? (I could possibly see it containing a list of all items in the meal with prices). Tax is almost always a percentage, but what about tip? Judging by the the above values, we can assume a 15% tip, but we don't know if the customer was stingy and tipped $0.15, and by just name alone, we can't tell at all.

    calc_total(meal_cost, tax_percent, tip_percent)

It's now immediately clear to me the type and range of values it accepts. The tip_percent is also an example of when a good name can provide info that even static typing could not, because in either case it is a floating point (please let's not get into a debate about Decimal or currency types :P ). This is a very basic example, but it applies at all levels. Don't call the parameter "users" if the function is not expecting an iterable of User objects. Maybe "usernames" would be better. Etc.

But of course, this only helps if the code you're working with is named well. In something like Java, you have better protection and tools when working alongside lower quality code. I also completely agree with you on point #2 about No Static Types. Navigating through my editor is so much easier in a static language than it is in PyCharm with large projects. And the most annoying thing is that autocomplete breaks with ORMs, and most ORM usage is actually flagged as a warning or error. Ugh.

I also feel very confident in the automated refactoring in something such as an IntelliJ Java project, or ReSharper, but am apprehensive about using PyCharm to refactor anything with usages spanning more than one file. Same goes for Javascript (or any other dynamic language, I suppose. Those are just the two I use).

Enjoyed the posts by the way, adding your blog to my reading list.

The example you mentioned, translated in Java, would be:

    Double mean = 55.50;
    Double tax = 0.0675;
    Double tip = 0.15;

And the function declaration would be:

    Double calc_total(Double meal, Double tax, Double tip)

So even with the types, you have exactly the same problem as in python, and creating a special class to wrap up percentages is something I find quite heavy.

Your alternatives would be to have naming conventions, like you do, or some proper documentation that tells you what the function expects for its arguments, with an example of a function call, which I particularly like in python because of the REPL.

But perhaps a better type system can still be helpful. E.g. F# supports units of measure, so you can declare 'dollar' as a unit, and write

    let calc_total (meal_cost : float<dollar>) (tax : float) (tip : float) =
       meal_cost * (1.0+tax) * (1.0+tip)

This way it is at least clear from the types that the numbers are meant to be multiplied, not added.

I never used F#. In your example, would the code:

    meal_cost + tax

trigger a compiler exception?

Yes, you get

    The type 'float' does not match the type 'float<dollar>'

There is an online typechecker, so one can try out F# without installing it: http://www.tryfsharp.org/Learn/scientific-computing#units-of...

I am sad GIT got widely adopted. GIT-SVN was almost superpower a few years ago. :-)

There was a nice 10 year overview of git linked from the article https://www.atlassian.com/git/articles/10-years-of-git/ I think Atlassian are great sports for featuring GitLab (that competes with their Bitbucket and Stash products) in there, thanks!

Kind of a nitpick, but that infographic shows that in 2014 Git was used by 33% of developers. Atlassian didn't say which source that came from, but I'm going to guess it came from a 2014 Eclipse Community Survey of 876 respondents[1][2].

I found the poll a bit misleading. There were separate categories for Git and GitHub, but AFAIK you were only supposed to choose one. I'd wager most of the GitHub users are also using Git, so the graph would look more like this[3].

[1] http://www.slideshare.net/IanSkerrett/eclipse-community-surv... [2] http://eclipse.dzone.com/articles/eclipse-community-survey-2... [3] http://i.imgur.com/CEkIHSQ.png

Jesus, so Torvalds built the MVP for git in 1 day and pretty much scaled it up for kernel usage in 10 days. Now, as a humble average developer, how do I achieve Torvaldian levels of productivity?

99% of the time I use:

- git status

- git add ...

- git reset ...

- git commit ...

- git log ...

- git push/pull ...

I guess that's "the basics" - what command should I learn next?

git rebase -i Very useful!

Yes, but watch out if you've already pushed to remote branches or even done merge/rebase with other local branches. You're rewriting history.

I most often use it because I forgot to include a certain file in my most recent commit. I'll just commit that file then rebase -i to merge the two.

Command to learn: - git rebase (if you learn everything you can do with this command, you'll pretty much know git inside and out)

Other useful stuff: - git diff - git diff --cached - git log --graph --decorate --pretty=oneline --abbrev-commit --all - git cherry-pick - git stash

I use this command constantly:

http://blog.kfish.org/2010/04/git-lola.html

Being able to see the graph structure made it far easier for me to get a grasp git's general structure and flow on a higher level.

Somewhat off topic, but I'd love to see something more git-like that works for large repositories. I work on video games and our repos are several TB. It's not practical to use git in those situations and Perforce feels too clunky to me.

Have you tried git-annex? It handles large files really well and is as close to git-like as you can get. :)

I haven't tried it, but I've looked at it. I think it adds too much complexity. Who decides which files go on the annex and which don't? Doesn't seem like an automated great solution for a scale-able team.

I'm looking for something more like CVS/Perforce where you can check anything in, but then with a more Git feeling interface. What I'd really like to do is to look at Git feature by feature and build the closest thing possible that does not include cloning the entire history locally under normal use. I know that is the fundamental paradigm of Git, but it seems that something closer to a hybrid of Git and Perforce could be created. Not sure exactly what it would look like. It's just jarring to jump from Perforce/CVS to Git and I don't think that's completely due to the local repository model. It's how branching works, it's how merging works, etc.

I wonder if BitKeeper owner Larry McVoy has ever regretted not open sourcing his software? Git tools is a whole industry now. The most promiment one, github, recently become one of the 100 most popular websites on the planet.

Regret it? Sure. I'd do it in a heartbeat if I could figure out how to make it work. Still would and there is plenty in BK that Git doesn't have. Like submodules that actually work exactly like a monolithic tree, just lets you clone what you need.

But we've never figured out how to make it work financially. If anyone has any ideas I'm all ears (though pointing at github and saying "do that" isn't an idea that I can execute).

BTW, BK used to be pretty darned close to open source, you got the source code under a funky license that said "don't take out the part that lets us make money". We stopped shipping the source when we learned that the very first thing that someone committed to the repo was taking out the part that let us make money.

  > Sure. I'd do it in a heartbeat if I could figure out how to make it work. 

just upload it to github. :)

Very cool of you to share your thoughts. I sympathize with your dilemma. It seems that the people who end up making money out of free/open source software are often not the ones who write the code. And I remember reading back in the day that Linus would talk with you extensively about the nuts and bolts of DVCSs, so I'm sure all git users owe you some gratitude for inspiring him to create git and getting the fundamentals right from the get go.

Out of curiosity, and please feel free not to answer, is BK still a viable commercial product bringing in significant revenue? And what obstacle do you see with going the platform/service route like github? I assume that's something you've seriously considered, even without open sourcing BK.

Yeah, BK still pays the bills for our team. We're small though, I recently found out that perforce has around 250 people, we're less than 1/10th that. But we pull in millions a year, enough to pay our people above scale even in the bay area, so far, so good.

I'll admit we've fallen off the radar (well, we were never really on the commercial radar, the only "marketing" we ever did was getting Linus to use it and that wasn't intended as marketing, it was intended to keep the kernel from diverging like the BSDs did. But it turned out to be a form of marketing that has kept us alive).

We're gonna try some actual marketing. Stay tuned. We'll probably screw it up :) But we hired a marketing company, I've gone back to writing papers, we'll give it a try. If you have ideas on how we can put ourselves back out there, we'd love to hear them.

As for viable, heck yeah. We work well on big repos (better than git), we've got what we call nested collections of repositories (did I mention I suck at marketing, yeah, I came up with what to call it) that are sort of like submodules except they work exactly like a single repo, sideways pulls work, anything that works with one repo works with N repos, that includes all the guis, command line, everything. We've got an answer for binaries that works for gaming companies. We've got a sane user interface (that's what Mercurial copied, in a somewhat sketchy way).

Git is sort of like the wild west, it never met an idea it didn't want to implement (at least partially). We're more enterprise ready (yeah, over used term) in that we work hard to make sure that BK has all the guard rails, seat belts, etc, so that you can deploy to people who could care less how any SCM works and they don't drive themselves over a cliff. Definitely less cool than git in that we take away some (bad) options, but safer.

We have seriously considered open sourcing a version of BK. We've been doing a lot of performance work and we essentially have two BK's, the almost SCCS compat ascii format slow version (slow but any version of BK will talk to it), and the fast one with a new binary file format (stuff like show the top commit comments are 35x faster in the linux kernel, that number goes up as you add more csets). We considered open sourcing the slow one but that effort has stalled. It could be revived, it just has to be worth it to us.

The github ship, in my opinion, has sailed. Maybe we could have open sourced BK back before git and done a github thing but it's all flashy UI stuff and we sort of suck at that. We're really good at systems stuff (you'll see when we start doing marketing, we scale, git doesn't) but flashy? Not so much. We do our UI in tcl/tk (I know, I know, but we have one UI person who makes it all work on windows/linux/macos and tcl/tk is a big part of that. At least we wrote a C like language that compiles to tcl byte codes so we're out of tcl. Thank God.)

Wouldn't the standard open source-as-freemium work? i.e. a free open source version with enough cool features (e.g. nested respositories), but not efficient. It's free marketing to keep you on the radar, that targets the people who appreciate your systems chops (and, like Atlasian, also gets it in under the radar, to developers). Enterprise customers happily pay ridiculous sums for full versions. And git/hg makes you immune to the competitive danger of open source clones.

I'd value your thoughts on this, as I also have a popular open source competitor, that followed me. The strategy seems sensible, but it might undermine perceived value; and it's a hassle to maintain two versions...

Also, can I please ask a technical BK question: How much does git differ from BK internally? i.e. git has graphs of commits, content-addressable for efficient checks of identity and integrity. Did git get any of that from BK? Or was it more the workflow and distributed concept of everyone having a copy of the repository? Many thanks!

Linus definitely did his own thing with git. The general ideas came from BK, BK gave you clone/pull/push/commit as the model. Everyone copied that because it just makes sense. The all or nothing clone model came from BK.

How it is all glued together differs quite a bit. BK has the concept of a revisioned file, git does not, it versions trees. That's why Linus thinks renames are silly, he doesn't care about them, he cares about the tree.

The graphs of commits comes straight from BK, that's BK's changeset file - which is sort of neat in that it is a version controlled file itself. BK is the only system that I know of that uses a versioned file to store the metadata.

OK, so on the business model thing, I'm not sure. The way we did the old compatible format is compatible but it's pretty slow, it converts to the new format in memory and then converts back if you write it out. It's slower than the older implementation (but this way we have one in memory format, less bugs). I thought it was good enough for small projects, my team overrode me and said "too slow".

As for enterprise customers "happily paying", um, no. We constantly get wacked with "if you don't do this or that we're moving to git". Which could be viewed as a good thing, we have to keep making it better, but it gets tiresome.

Thanks! Renames make archeology difficult in git. I've become reluctant to change {file,directory} names, even when it's clearer...

BTW: What are the benefits of versioning changesets themselves? Isn't it rare to only change the changeset?

Chained conversions are elegant, but slower code is unsatisfying... I guess such hobbling is the essence of open-source-as-freemium. :(

I meant they "happily pay" for full over free versions. (For them, it's also paying for "new" features!)

Renames are a thing and git made the wrong choice there. It's not like we are perfect but we are way closer.

So on versioning changesets I didn't really explain. Lemme try again.

In any DVCS you have a bill of materials, that's what describes the tree. Git's is different than ours because they don't version files, we do. So our bill of materials looks like:

  path/to/file <version>
  path/to/different_file 1.1
  path/different_dir/a_file 1.19

If you "cat" the changeset file as of any version you get what the tree looks like, a list of files and a list of revisions.

Of course it doesn't work like that because, um, reality and merges and parallel development. We have UUIDs for each file and each version so it looks like

UUID_for_a_file UUID_for_a_version

and our UUIDs are pretty sweet, not sha1 or some other useless thing, they are

user@host|path/to/where/it/was|YYYYMMDDHHMMSS|checksum

those are for each node in the graph, for the very first node which is the UUID for the file, there is a "|<64 bits of /dev/random>" appended.

So the changeset file is just a list of

UUID UUID

Not sure if that helps.

The benefit of versioning the file that holds all that data is we can use BK to ask it stuff. Want to see the history of the repo? bk revtool ChangeSet Want to see what files changed in a commit? bk diffs -r$commit ChangeSet Yeah, we have to process all the UUIDs and turn them into pathnames and revisions but we can do that and do it fast. So it works.

All the tools we built to look at stuff can look at the metadata. That's worked out well.

I wrote an article a few months ago summarizing where Git is in 2015 if anyone is curious[1]. Most developers at my company don't seem to want to learn a "new" SCM so we're stuck with SVN (or CVS for some projects).

We rarely have a stable trunk. Branching takes too long so most people don't want to do it. Merging two branches is such a scary thing that people avoid branching in the first place. Or I've seen them copy code from one branch in one Eclipse window and paste into another separate project (on another branch) in another Eclipse window. They repeat this manually for the next 5 to 20 files. I don't think they've realized a merge can often be as simple as a button click or one SCM command. But hey, it works for them.

The one time on my team that someone was interested in exploring Git was when we couldn't find an up-to-date Maven SCM connector for SVN that played nicely with Eclipse. The solution? Use an older version of Eclipse.

[1] http://www.netinstructions.com/the-case-for-git/

off topic: is the there a third party service that will let me collapse all sub-comments and just read the parent comments?(and then expand them if they seem interesting?)

There's API for HN (https://github.com/HackerNews/API), it's not that hard to make one yourself. This is Hacker News after all.

One thing worth saying here is that Git is now the dominant player in the source control market. According to almost every survey I've seen, it's overtaken Subversion (according to some reports by a fairly large margin) not only for open source and hobbyists but in the enterprise as well. It's more or less become a lingua franca for communicating source code between teams these days, as well as being the preferred deployment option for many cloud hosting providers and even some package managers. No other source control system has ever managed that.

As such, you simply can't afford not to know it these days. In fact, I can't help thinking that not using Git should now be a major red flag for job candidates and prospective employers alike. Sure, not using your favourite tool may not be that big a deal, but not using what is to all intents and purposes the lingua franca of source code communication is a serious omission.

I wish Linus would now turn his attention to: 1) make (ought to be a simple concept but never seems like it's quite been done right) 2) init (only he has the clout to solve the pid 1 controversy) Will check back in 2025 for progress report.