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Re: [Gnu-arch-users] Arch Versus CVS Versus Subversoin
From: |
John A Meinel |
Subject: |
Re: [Gnu-arch-users] Arch Versus CVS Versus Subversoin |
Date: |
Sun, 05 Dec 2004 20:09:30 -0600 |
User-agent: |
Mozilla Thunderbird 0.9 (Windows/20041103) |
Andrew Suffield wrote:
On Sun, Dec 05, 2004 at 07:27:37PM -0600, John A Meinel wrote:
Andrew Suffield wrote:
On Sun, Dec 05, 2004 at 02:59:32PM -0600, John A Meinel wrote:
Yes, arch supports binary diffs in exactly the same sense as subversion.
It doesn't do delta compression on them. That's irrelevant.
It is not irrelevant, people care about it.
xdelta is not a diff. It's delta compression. That's even in the *name*.
This is most definitely NOT what the original poster was meaning by
"binary diff".
You mean they were out of their tree and using the wrong names for
things? You'll never get anywhere like that. "$foo diff" is an
operation which generates the input to "$foo patch", such that:
patch(A, diff(A, B)) == B, where A and B are of type $foo
That's the definition.
This is the first time that I've heard it (properly) called delta
compression.
Compression is not related in any way.
compression is not binary diff. True. But the reason people want binary
diff is so that when you have your 10MB Word document, and you change 2
lines in it, when you do the commit it doesn't have to upload 10MB of
data.
No, the reason people want binary diffs is so that they can have
binary files stored in revision control. That's what it means and
that's what it does.
I do believe that what the original poster was asking for was "binary
deltas". Yes we support "binary diff" as you name it. Your terminology
is probably better than mine. But CVS has long supported binary files,
what people didn't like is that every time they made a change, the size
of their repository went up by the complete file size, instead of just
the differences. The reason every one else calls it a binary diff is
because a normal diff only contains the changes, your version of a
binary diff contains the entire file pre and post.
Yes, I understand why it does that. And I'm not really advocating that
it changes. I might argue that we would be better off storing the md5sum
of the previous version rather than a complete copy of it, but generally
that is irrelevant.
The only reason I can think of to use SVN is if I ever try to revision
control a lot of binary files. Think most office document formats. MS
and OOo. (ooo is zipped xml, but you are still committing the zip file
which is binary)
Admittedly, I'm talking about a small population (about 10+ people), but
when I was taught CVS I was warned that binary files are not "diffed"
but store in complete form each time. (Obviously this should have been
"delta compressed"). I have also heard this argument from independent
sources (as mentioned, about 10 times). I realize all of us are using
the wrong terminology here. But I know that is what they meant, because
the complaint was about the size of the archive, and how much better SVN
is because it only stores the changes.
See here:
http://osdir.com/Article203.phtml
Subversion stores all files in a binary representation and uses an efficient
binary diff algorithm to compute differences between them. This means multiple
revisions of binary files take up a lot less space on the server
"efficient binary diff" => delta compression.
John
=:->
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- [Gnu-arch-users] obtaining delta compression with 1.x (was Re: Arch, CVS, Subversion), (continued)
- Re: [Gnu-arch-users] Arch Versus CVS Versus Subversoin, John A Meinel, 2004/12/05
- Re: [Gnu-arch-users] Arch Versus CVS Versus Subversoin, Andrew Suffield, 2004/12/05
- Re: [Gnu-arch-users] Arch Versus CVS Versus Subversoin,
John A Meinel <=
- Re: [Gnu-arch-users] Arch Versus CVS Versus Subversoin, Andrew Suffield, 2004/12/05
- Re: [Gnu-arch-users] Arch Versus CVS Versus Subversoin, John A Meinel, 2004/12/05
- Re: [Gnu-arch-users] Arch Versus CVS Versus Subversoin, Andrew Suffield, 2004/12/05
- Re: [Gnu-arch-users] Arch Versus CVS Versus Subversoin, John A Meinel, 2004/12/05