>> Given that it's the repository format used by Linux developers, I think
>> it's safe to say it works adequately for multiple people editing the
>> file in parallel.
>
> This boggles my mind. Apparently I /don't/ understand how Git works at
> all...

Perhaps I can summarise:

The Darcs workflow. I download the source code, make a small edit to it, 
ask Darcs to record that, and send the changes to the developers. They 
add it to the central repo, which checks whether the bit I just edited 
has changed since I got my copy. If not [which is quite likely], the 
change is added to the central repo. Done.

The Git workflow. I download the source code, make a small edit to it, 
and ask Git to record that. Git takes a complete record of every file in 
the entire repo. I send that to the developers, and they try to add it 
to the central repo, which makes Git check whether any unrelated changes 
have happened anywhere in the entire repo since I made my change. Since 
it is 100% guaranteed that this will have happened, the merge fails. I 
now have to download the latest version of the source code, do a bunch 
of work on my end to incorporate my 3-line edit into the newly updated 
source tree, record a completely new commit object, and send that plus 
the previous one back to the developers. They try to merge, find the 
exact same problem, and I have to repeat all the above steps. We repeat 
this endlessly until, by some fluke, I manage to execute the entire 
download / merge / commit / send / have the developers merge cycle 
without anybody else successfully merging to the central repo in 
between. When this happens, instead of the 3-line change being added to 
the central repo, we get a 25-mile string of merge commits plus the 
actual 3-line edit at the beginning.

FTW, people?

Obviously this model cannot possibly work, so there must be something 
I'm misunderstanding about how Git works.

Post a reply to this message

Darren New <dne### [at] sanrrcom> wrote:
> Having spoken with half a dozen people who said "I hate git, it's so 
> confusing" and then after showing them this they go "wow, that's really 
> easy", I figured it might be worthwhile to show people this. :-)

  I hate SVN. SVN projects are so easy to break accidentally, and if you
don't know the exact reason, you could be fighting to fix it for a long
time.

  SVN projects are extremely fragile. SVN has the totally braindead idea
of putting a .svn project directory on each single subdirectory in the
project. (This is very unlike git, which keeps one single project directory
under the main directory where the project resides.)

  For example, duplicate a directory with your favorite file manager.
Oops. SVN doesn't like that new directory at all. It refuses to add it
to the project, or do anything at all with it. If you don't know why this
happens, you are stuck. SVN refuses to do anything with it. (Solution:
Remove the .svn subdirectories from the entire offending directory hierarchy.
Most graphical file managers have no support for doing this recursively, of
course, and it's aggravated by . files being hidden in unix systems.)

  Copy the contents of a directory (and its possible subdirectories) from
somewhere else (eg. update the contents of a third-party library, or copy
the work you have been doing on another platform to the project). Oops,
you just broke SVN once again. SVN will once again refuse to do anything
with this directory. You can't commit, and even an update won't fix the
problem. (Solution: Remove the entire offending directory structure, then
update, then copy the individual files from the other directory, rather
than the entire directory structure.)

  Sometimes renaming/moving things from an SVN client itself can break
things, even though it shouldn't.

  On a Mac the file system adds an additional layer of annoyance. Try
changing just the case of a file name (for example change "settings.hh"
to "Settings.hh") and try to figure out how to make SVN work after that.
It can be a pretty fun evening. (Not.)

-- 
                                                          - Warp

Post a reply to this message

On 4/21/2011 1:17, Invisible wrote:
> If you don't want
> changes you've made, you either record commits reverting them, or you just
> delete them from the history outright.

OK. It wasn't obvious from the bits I read that it was easy to delete 
changes from the repository. I guess Darcs probably does that better than 
mercurial or something.

> Well, yes, if you delete all your work, you have a problem. This isn't
> unique to Darcs. I'm not seeing what your point is...

That the solution to deleting branches you're in the middle of working on is 
the same in both cases: "Duh, don't do that. Or make backups."

-- 
Darren New, San Diego CA, USA (PST)
   "Coding without comments is like
    driving without turn signals."

Post a reply to this message

On 4/21/2011 2:26, Invisible wrote:
> You can still apply whatever tools you want to your files, no matter which
> way you store them. Although I will admit, having a diff algorithm built
> right into the version control software is quite nice. (Although sometimes I
> wish Darcs did this better.)

That's exactly what I mean. In order to have Darcs do this better, you have 
to actually fix your repo to use the better algorithm. In git, the algorithm 
isn't part of the repo. It's only part of the tools. Your very statement 
"it's built in, but I wish Darcs did it better" is exactly my point.

> If you just write "darcs diff", you can see the changes between any two
> versions of your repo.

What if I want to use kdiff3 or gvimdiff or some other diff visualization tool?

>>> OK, wow. I thought having to tell Darcs when I rename stuff was
>>> inconvenient, but this just sounds insane...
>>
>> Why? You don't have to tell git you renamed something.
>
> Which means that it tries to guess when you rename something, so it is 100%
> guaranteed to guess wrong sometimes.

If a file disappears from one place and at the same time reappears somewhere 
else with exactly to the byte the same contents, does it really matter 
whether you renamed it, whether you cut and pasted, or whether you typed it 
back in?

Remember, git is storing snapshots of the repository, not changes. The fact 
that something got renamed is sort of irrelevant.

Darcs is also storing snapshots, except snapshots of changes. If I rename 
file A to B, and then from B to C, and *then* I commit, Darcs isn't going to 
have those changes either.  If I delete five lines, then another ten, then 
commit, Darcs is going to lose that history that that was actually two changes.

> Yeah, it's unclear how you can hope to version control a binary file, other
> than just keeping a linear sequence of versions (which is what Darcs
> apparently does). Personally I've never needed to try, but I guess somebody
> I might.

Word documents. Images. Audio. Video game resources. People want version 
control for all of that.

Keeping all the old versions is the way to do it. The problem comes when you 
have a distributed repo, and you have to store locally every old version of 
all the binary files that you almost never are going to want.

Imagine if you were a Linux developer and people stored installation CD ISO 
images in the repository. Do you really want to check out every copy of 
every install CD just so you can fix bugs in one file system?

> I don't know, man, that all looks very, very complicated to me.

You asked what happens in that case. That's what happens.

> If I want to fix a bug in (say) GHC [which uses Darcs], I find the files in
> question, edit them, record the changes, and email the file to the GHC
> developers. I don't need to care about branches or whether the development
> tree has changed since I got my copy of it. They don't need to care whether
> my repo is in sync with theirs. They just apply the change, and it's done.
> Simple.

That's how it works with git also. Indeed, there's a git command that says 
"generate an email with the patch in it that I need to update someone else's 
repository."

You are making a branch. Your whole repository is a branch of the other 
guy's repository. If you look at the up-pointing lines as "you mail me a 
patch", then you get the same answer.

You asked what happens when someone keeps working on a branch that someone 
else already incorporated. I showed you how git decides which diffs to apply 
and which not to apply. Darcs does the same thing when building the working 
directory. It's going to apply the new patches, but how does it know what 
the new patches are? Right, it goes back until it finds the patches it 
already applied, then applies the newer ones.

>>> Git doesn't support recording half a file modification,
>>
>> Yes it does. Indeed, you can even go back and retroactively say "oh,
>> those two commits? The second one should have come first, and the first
>> one should be broken up into these three commits."
>>
>> As I said, I do this all the time.
>
> I don't see how that's possible.

Here's how to do it without the GUI:

http://book.git-scm.com/4_interactive_adding.html

With a GUI, you look at the patch list, right-click a hunk, and say "stage 
this to be committed".

If you want to change old commits, you do this:

http://book.git-scm.com/4_interactive_rebasing.html

Again, that's the text-based way of doing it without a gui.

>>> and doesn't even figure out which files changed.
>>
>> Yes it does.
>
> Then why do you have to manually tell it which files to commit?

Because maybe you don't want to commit all your changes in one step.

> I'm not sure I'm understanding what Git does. What Darcs does is show you
> each change and say "do you want to put this into the commit?" If you say
> yes, it records that change. If you say no, the change stays as "new".

In git, say you start with a working directory that matches the latest thing 
in the repository. You change files AA, BB, and CCC, and you add file DD. 
Changing the first two were to fix a bug, and the second two added a 
configuration option.

git add AA BB
git commit -m "fix bug"
git add CCC DD
git commit -m "add configuration option"

Let's say you then change 173 files, converting all single quotes to double 
quotes. You can then say

git add -a
git commit -m "change quote style"

> not sure what you mean by "Darcs needs you to do that all in one step".

I mean that gathering up the changes and committing them sounds like a 
single step in Darcs. In git, I can say

wings3d my_model.wings
git add my_model.wings
gimp my_image.jpg
git add my_image.jpg
vi configuration.ini
git add configuration.ini
git commit -m "add a textured model with some configuration"

>> The staging area lies between the repository and the working directory.
> So, wait, there's a third file storage area?

Yes. That's where you build up the next commit. It's called the staging 
area, or the index.

>> Then I use something like "git add" to add all the changes from the WD
>> to the staging directory. Or I use "git add -i" (or, more likely, the
>> GUI) to diff the WD against the staging area (or the repository), pick
>> (say) three of the five diff hunks, and then create a new temp file that
>> holds the repository with those three diff hunks applied, which I then
>> put in the staging area. When I have everything the way I like, I commit
>> the change, which copies the staging area into the repository and then
>> adds a commit object pointing to it.
>
> Damn that sounds complicated.

It's very simple with the gui. You start up the gui, it shows you a top-left 
pane of files that have changed that you haven't decided to commit yet. 
Bottom right pane are files that'll be in the commit. Right side is the 
listing of the diffs for whatever file you've highlighted.

If you want to put half the changes from configuration.ini in your commit, 
you click on that, go over to the list of diffs, click on each one you want 
in the commit, then click the commit button.

Pretty trivial.

>>> This boggles my mind. Apparently I /don't/ understand how Git works at
>>> all, because the way it seems to work precludes two people touching the
>>> same file at the same time...
>>
>> Sure. But you're thinking git tracks diffs. That's exactly the point.
>
> I know Git doesn't track diffs - I just can't comprehend how that can
> actually work properly.

Because files are actually named by their SHA-1, so nobody ever touches two 
different copies of the same file at the same time.

>> If
>> I change the file, and you change the file, then now there's three
>> files. The original, the new one I have, and the new one you have. When
>> we go to merge it, we create number four, which is your new one with the
>> differences between my version and the original applied.
>
> This just seems a very strange way to look at things. Generally you don't
> care about versions, you care about alterations. "Does this draft have the
> corrections to chapter 4 in it or not?"

And you can trivially tell that in git, not by looking at the files, but by 
looking at the commits.

> It seems to me that with the Git model, any time anybody edits any file, you
> create a new version of the entire repo that then has to be laboriously
> merged back into everybody else's repos. (Assuming no other edits have
> happened in the meantime.) What a clunky way to work.

It's not laborious to merge it in, any more than it's laborious to merge 
changes in Darcs into your repository and working directory.

If I clone a repository from you, your repository's URL is stored in my 
repository and called "origin" (by default). If I want to fetch all your 
changes, I say "git pull origin", which connects to your repository, gets 
the list of objects you have that I don't, and pulls them down. It also 
updates any branch names that you changed since last time I did that, so if 
you have a branch called "bugfix", I'll have a branch called 
"origin/bugfix". If Sally also cloned your repository and created a branch 
called bugfix, then I pulled from Sally also, I'll have a branch called 
"origin/bugfix" and one called "sally/bugfix".

>>> And the "minor detail" that if 200 people edit the same file, that's 200
>>> separate branches which have to be manually merged back together again.
>>
>> And this differs from any other VCS how?
>
> With a centralised system, usually it's a check-in / check-out model, so
> only one person can edit a file at once.

Um, no, not for the last 15 years or so. Not even CVS did things that way, 
let alone SVN.  Some systems work like that, yes, but they work really, 
really poorly when you have 200 people working on the same files, which is 
why people moved to CVS in the first place.

> With something like Darcs, there are now 200 change-sets, each of which is
> only in some repos. Copy the change-sets around and everything is in sync
> again. No need for complex "merge" operations or tangled file histories.

Of course you need to merge them, and of course you'll have tangled file 
histories. If all 200 people change the same part of the file, you'll have 
200 merge conflicts. If everyone is passing around partial change sets and 
making more changes that are dependent on those changes, you'll have a 
tangled file history.


>> Note that if you're trying to *push* changes to a remote repository, you
>> have to do it to a branch where nobody else has branched off since you
>> did.
>
> And what the hell are the chances of that ever happening? If every time
> anybody touches any file it generates a new branch, then there's no chance
> of ever being able to push changes back.

http://www.kernel.org/pub/software/scm/git/docs/git-rebase.html

Basically, you say "go look at the changes I made since I branched off the 
upstream repository, then apply those same changes to the new head of the 
upstream repository, and submit *that* as the new commit."

> And hope that the DEV branch doesn't change while you're busy trying to
> catch up. Still, I suppose if you repeat this cycle enough times, eventually
> you might get lucky and be able to perform the push.

If the DEV branch is changing that quickly, it means *someone* is going 
through this cycle successfully.   You're complaining that nobody goes to 
that restaurant any more because it's always too crowded.

The rebase is a single step, unless there are merge conflicts, so it's 
basically bound by network and CPU.

>>>> If you want to merge someone's repository into yours, you simply copy
>>>> from them any files or names that they have that you don't, and you're
>>>> done. You're merged.
>>>
>>> It would be nice if Darcs worked that way.
>>
>> Right. In Darcs, you have to merge all the changes. In git, you have to
>> merge all the changes.
>
> No, I meant it would be nice if the Darcs repo format allowed you to update
> a repo just by copying some files.

Well, git *does* store stuff in files, so technically you could copy the 
files. But by "copy files" I mean "use git to copy the new files."  As in, 
"you don't have to run any diffs or patches or anything".

> Darcs also doesn't explicitly support the "bare" format that Git does,
> despite it being obviously useful.

Which is why you don't have trouble with the rebasing. You only need to 
rebase stuff when you're pushing to a bare repository without human 
intervention. Basically, if you're sending changes to a bare repository 
without human intervention, you have to prove you've already resolved the 
merge conflicts that such might impose on someone else who later updates 
from that bare repository.

>>>> Now if you want to incorporate their changes into
>>>> your work, you generate a diff between their latest version and some
>>>> earlier version, and apply that diff to your latest version, and you're
>>>> merged.
>>>
>>> What a backwards way to look at it.
>>
>> Only if you're used to looking at source control as a series of diffs to
>> start with. But that's (A) exactly what makes git hard to understand and
>> (B) exactly what makes git brilliant. :-)
>
> So doing things the hard way is brilliant?

Building an entire type theory to discuss isomorphic idempotent change sets 
is the easy way?

-- 
Darren New, San Diego CA, USA (PST)
   "Coding without comments is like
    driving without turn signals."

Post a reply to this message

On 4/21/2011 2:35, Invisible wrote:
>>> Given that it's the repository format used by Linux developers, I think
>>> it's safe to say it works adequately for multiple people editing the
>>> file in parallel.
>>
>> This boggles my mind. Apparently I /don't/ understand how Git works at
>> all...
>
> Perhaps I can summarise:
>
> The Darcs workflow. I download the source code, make a small edit to it, ask
> Darcs to record that, and send the changes to the developers. They add it to
> the central repo, which checks whether the bit I just edited has changed
> since I got my copy. If not [which is quite likely], the change is added to
> the central repo. Done.

That's exactly how git works, workflow-wise, if you want.

http://book.git-scm.com/5_git_and_email.html

You *also* have the option of telling the other guy the URL of your 
repository and having him suck it in, or an option of pushing to a (possibly 
bare and unattended) repository your changes.

> The Git workflow. I download the source code, make a small edit to it, and
> ask Git to record that. Git takes a complete record of every file in the
> entire repo.

Uh, no. Not if you're doing it manually. If you're automating it by cloning 
the repository or pulling and pushing changes over git protocols without 
human intervention, then yes. But since your repository tracks what you got 
from other people, you already know about changes you made that they don't have.

> I send that to the developers, and they try to add it to the
> central repo, which makes Git check whether any unrelated changes have
> happened anywhere in the entire repo since I made my change. Since it is
> 100% guaranteed that this will have happened, the merge fails.

Wow. Advice: Don't talk to anyone about how git works, since even if you 
think you've figured it out, you haven't.

> Obviously this model cannot possibly work, so there must be something I'm
> misunderstanding about how Git works.

Ah, thank you.

Yes. You're thinking that you can't add a commit to a repository without 
merging it in. You're still thinking there's one authoritative set of files. 
There aren't. There's bunches of snapshots.

So when you send your change to the maintainers, you're sending them new 
files. There are no merge conflicts, because there is no merge. Every 
changed file has a new sha-1, so it's a new file. git can look at the 
repository and know where in your working directory each file belongs 
(because some of the files in the repository are directories), but in the 
repository itself it's all just a big flat bag of sha-1 files.

So sending your changes to someone else doesn't cause merge conflicts, and 
there's no need to back them out.

When I want to put your changes into *my* version of the files, I have to 
merge it, just like Darcs.

The equivalent description would be that if you changed something in Darcs 
nd I made a change in my working directory, you could no longer send me 
patches until I threw away all my working-directory changes, in case there 
was a conflict.

-- 
Darren New, San Diego CA, USA (PST)
   "Coding without comments is like
    driving without turn signals."

Post a reply to this message

On 4/21/2011 7:46, Warp wrote:
>    I hate SVN. SVN projects are so easy to break accidentally, and if you
> don't know the exact reason, you could be fighting to fix it for a long
> time.

I agree. I've *never* gotten an svn branch to merge back. I have *always* 
built a patch, and then applied the patch to the head.

>    SVN projects are extremely fragile. SVN has the totally braindead idea
> of putting a .svn project directory on each single subdirectory in the
> project. (This is very unlike git, which keeps one single project directory
> under the main directory where the project resides.)

While it lets you check out only parts of the project, it's a PITA to deal 
with. Especially when you want to recursively grep your code for the last 
vestiges of variable abcxyz, and it's all over inside the files under .svn.

git doesn't do that because a git repository is basically a big flat bag of 
files with no possibility of conflicting file names, so there's no 
subdirectories possible. :-)

But yah, all that stuff is a pain. I wound up having to toss and check out 
the entire local copy at least once a month at work, just because crap would 
break and I couldn't fix it locally.

-- 
Darren New, San Diego CA, USA (PST)
   "Coding without comments is like
    driving without turn signals."

Post a reply to this message

On 4/21/2011 2:35, Invisible wrote:
> The Darcs workflow. I download the source code, make a small edit to it, ask
> Darcs to record that, and send the changes to the developers. They add it to
> the central repo, which checks whether the bit I just edited has changed
> since I got my copy. If not [which is quite likely], the change is added to
> the central repo. Done.

OK. All the confusions you think you're seeing in git are due to Darcs just 
not being able to do what git does.

When Darcs gets a merge conflict, it just doesn't apply *either* patch.

"Darcs escapes this problem by ignoring those parts of the patches that 
conflict."

Obviously, if Darcs isn't going to try to fix the patches for you, it's a 
lot easier to record a bunch of conflicting patches. The equivalent in git 
is to pull in changes from other repositories and then not trying to update 
your working directory to include the changes. Trivial one-liner that always 
works.

"If the conflict is with one of your not-yet-published patches, you may 
choose to amend that patch rather than creating a resolve patch."

And that's exactly what the "git merge" command does. It takes your patches, 
and someone else's patches, and merges them together. It's a separate step 
because, unlike Darcs, git supports having more than one "pristine" in the 
same repository. If you only have one branch in git, it's as trivial as only 
having one repository in Darcs.

"This is how a project with many contributors, but every contribution is 
reviewed and manually applied by the project leader, can be run." This is 
the bit about sending email you were talking about. git can work that way, 
and the terrible "merge" problems you're talking about are handled the same 
way: the guy getting the patches fixes the merge.

What Darcs apparently can't do is support any way of doing distributed 
development with an authoritative repository *without* someone dedicated to 
fixing the merge conflicts. That's where the whole rant you're talking about 
came from. If you have someone who is going to look at your changes (i.e., 
if I am CTO and I want to build a new release or something) then the whole 
"fast-forward merge with a rebase" dance is unnecessary and indeed 
counterproductive, as it loses the history of the change (in the same sense 
that unrecording a bunch of changes and re-recording one big change in Darcs 
loses the history).

I'll grant you that Darcs is definitely simpler, but I think it's less 
capable also, and that's the primary place the simplicity comes from. The 
Darcs replace command is interesting, but I'm not sure how well that would 
work in practice, especially in languages with complex scoping.

-- 
Darren New, San Diego CA, USA (PST)
   "Coding without comments is like
    driving without turn signals."

Post a reply to this message

>> If you just write "darcs diff", you can see the changes between any two
>> versions of your repo.
>
> What if I want to use kdiff3 or gvimdiff or some other diff
> visualization tool?

Then yeah, you'd have to construct two versions of the repo, just like 
you would with any other version control system.

>> Yeah, it's unclear how you can hope to version control a binary file,
>> other
>> than just keeping a linear sequence of versions (which is what Darcs
>> apparently does). Personally I've never needed to try, but I guess
>> somebody
>> I might.
>
> Word documents. Images. Audio. Video game resources. People want version
> control for all of that.

Trying to use version control for Word documents would be a fairly 
insane thing to do. (Unless you can actually parse the binary file and 
ignore all the metadata...) But sure, I can see how if I was doing 
something other than writing text, I'd probably want to version control 
that too.

> Imagine if you were a Linux developer and people stored installation CD
> ISO images in the repository. Do you really want to check out every copy
> of every install CD just so you can fix bugs in one file system?

Man, version controlling a multi-GB ISO image sounds like a barrel of 
laughs. o_O

>>>> and doesn't even figure out which files changed.
>>>
>>> Yes it does.
>>
>> Then why do you have to manually tell it which files to commit?
>
> Because maybe you don't want to commit all your changes in one step.

So you have to manually remember what you changed? That seems rather... 
primitive. I much prefer the way Darcs does it (i.e., prompt you for 
which changes you want to include in this particular commit).

>> not sure what you mean by "Darcs needs you to do that all in one step".
>
> I mean that gathering up the changes and committing them sounds like a
> single step in Darcs.

A single interactive step, yes.

>> Damn that sounds complicated.
>
> It's very simple with the gui. You start up the gui, it shows you a
> top-left pane of files that have changed that you haven't decided to
> commit yet. Bottom right pane are files that'll be in the commit. Right
> side is the listing of the diffs for whatever file you've highlighted.
>
> If you want to put half the changes from configuration.ini in your
> commit, you click on that, go over to the list of diffs, click on each
> one you want in the commit, then click the commit button.
>
> Pretty trivial.

So Git has a GUI tool that lets you do what Darcs does natively?

>> With a centralised system, usually it's a check-in / check-out model, so
>> only one person can edit a file at once.
>
> Some systems work like that, yes, but they work
> really, really poorly when you have 200 people working on the same
> files

Presumably this is why everybody wants distributed version control now.

>> With something like Darcs, there are now 200 change-sets, each of
>> which is
>> only in some repos. Copy the change-sets around and everything is in sync
>> again. No need for complex "merge" operations or tangled file histories.
>
> Of course you need to merge them, and of course you'll have tangled file
> histories. If all 200 people change the same part of the file, you'll
> have 200 merge conflicts. If everyone is passing around partial change
> sets and making more changes that are dependent on those changes, you'll
> have a tangled file history.

Except that usually 200 people will be editing 200 different parts of 
the repository.

> Basically, you say "go look at the changes I made since I branched off
> the upstream repository, then apply those same changes to the new head
> of the upstream repository, and submit *that* as the new commit."

The Darcs model is "the bugfix for #5326 is *this* alteration". You can 
then apply that to whatever you want. (Unless the modified bit is 
altered, of course.) The Git model seems to be to do lots of extra work 
and then record it as a new item of data, which you don't actually need, 
but that's just hot Git works.

>> No, I meant it would be nice if the Darcs repo format allowed you to
>> update a repo just by copying some files.
>
> Well, git *does* store stuff in files, so technically you could copy the
> files. But by "copy files" I mean "use git to copy the new files." As
> in, "you don't have to run any diffs or patches or anything".

Oh, I see.

>> So doing things the hard way is brilliant?
>
> Building an entire type theory to discuss isomorphic idempotent change
> sets is the easy way?

After you've built it, yes. The theory is hard, but it makes using the 
tool easy.

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

Post a reply to this message

> Wow. Advice: Don't talk to anyone about how git works, since even if you
> think you've figured it out, you haven't.
>
>> Obviously this model cannot possibly work, so there must be something I'm
>> misunderstanding about how Git works.
>
> Ah, thank you.

Like I said, the way Git appears to work is utterly hopeless, so I must 
have got something wrong somewhere.

> So when you send your change to the maintainers, you're sending them new
> files. There are no merge conflicts, because there is no merge.

Right. Every time you edit a file, it's actually a new file.

> So sending your changes to someone else doesn't cause merge conflicts,
> and there's no need to back them out.

OK.

> When I want to put your changes into *my* version of the files, I have
> to merge it, just like Darcs.

1. Having a copy of someone else's changes is useless unless I can 
incorporate them into the latest version of the files. This is the 
equivilent of three people taking copies of a file, editing it, and 
emailing me back three modified files. I don't want three files, I want 
*one* which has all the edits in it.

2. If I do "darcs pull", all new history is copied to my repo, and the 
working copy is updated to reflect these changes. [Assuming there are no 
conflicts of course.] That's it. That's all you have to do.

With Git, you have to do some crazy thing with comparing my working copy 
to the most recent common ancestor of my branch and the branch I'm 
pulling, creating diffs for that, comparing the most recent common 
ancestor to the snapshot I just pulled, creating a diff for that, 
combining the two diffs, and then applying that to the most recent 
common ancestor. You then have to *create a new commit object* 
representing this new combined state.

Every time you try to combine two states of the repo, it creates a new 
commit object representing the merge. Darcs, by contrast, lets me 
trivially apply any combination of changes I want. I can even create 
files with combinations of changes that have never existed before if I like.

I guess the thing that really flips my lid is that not only does Git 
require you to construct a useless merge commit every time you want to 
do something as trivial as put two changes together, but if you want to 
put new stuff into a repo, you have to somehow get the merge up to date 
first. That sounds increadibly fragile.

It also irritates me that Git insists that even unrelated changes must 
have a linear time ordering. Still, it's not like I actually have to 
*use* Git, so it doesn't really matter if I don't like it...

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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On 4/21/2011 13:07, Orchid XP v8 wrote:
> Then yeah, you'd have to construct two versions of the repo, just like you
> would with any other version control system.

Except git. Because git doesn't store diffs, it stores files. :-)  So it's 
trivial for git to run whatever you want against two different versions of 
the files.

> Man, version controlling a multi-GB ISO image sounds like a barrel of
> laughs. o_O

That's one of the reasons why people like centralized servers.

>>>>> and doesn't even figure out which files changed.
>>>>
>>>> Yes it does.
>>>
>>> Then why do you have to manually tell it which files to commit?
>>
>> Because maybe you don't want to commit all your changes in one step.
>
> So you have to manually remember what you changed?

No, of course not. Are you even reading what I'm writing?  Why would the 
fact that you tell git what changes you want to commit with one command then 
actually commit those with a second command mean that git can't tell what 
you changed?

> I much prefer the way Darcs does it (i.e., prompt you for which
> changes you want to include in this particular commit).

I prefer the GUI, actually. Much easier to pick out various commits to commit.

>>> not sure what you mean by "Darcs needs you to do that all in one step".
>>
>> I mean that gathering up the changes and committing them sounds like a
>> single step in Darcs.
>
> A single interactive step, yes.

Which means you can't (for example) stop in the middle when you realize you 
forgot to make one of the 30 changes you want to commit to fix something in 
particular. You have to start over.

> So Git has a GUI tool that lets you do what Darcs does natively?

It's native to git too. You get to use the command line or a gui. You're 
really not actually reading what I'm writing, are you?

> Except that usually 200 people will be editing 200 different parts of the
> repository.

And if that's the case in git, then you have no trouble merging things when 
and as you want them.

>> Basically, you say "go look at the changes I made since I branched off
>> the upstream repository, then apply those same changes to the new head
>> of the upstream repository, and submit *that* as the new commit."
>
> The Darcs model is "the bugfix for #5326 is *this* alteration". You can then
> apply that to whatever you want. (Unless the modified bit is altered, of
> course.) The Git model seems to be

The git model seems to be something you're still fully unfamiliar with.

 > to do lots of extra work and then record
> it as a new item of data, which you don't actually need, but that's just hot
> Git works.

What extra work? If you just want to commit everything you've changed, you 
say "git commit -all" or some such, and away you go. If you want to take my 
changes and update your repository, you say "git pull darren", and when 
you're ready to incorporate my changes into your development, you say "git 
merge darren".  It's two steps because you don't want to tie "get Darren's 
changes" to "make sure Darren's changes are all compatible with mine."

>>> So doing things the hard way is brilliant?
>>
>> Building an entire type theory to discuss isomorphic idempotent change
>> sets is the easy way?
>
> After you've built it, yes. The theory is hard, but it makes using the tool
> easy.

Honestly, I'm not sure I see any advantage of Darcs over git, other than 
possibly repository size. I imagine once you get enough change sets in a 
repository (think 10 years of Linux development), it could get really slow 
to check out a particular file.

-- 
Darren New, San Diego CA, USA (PST)
   "Coding without comments is like
    driving without turn signals."

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