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Re: [Axiom-developer] build-improvements on cygwin

From: root
Subject: Re: [Axiom-developer] build-improvements on cygwin
Date: Tue, 28 Nov 2006 12:26:56 -0500

> "GIT only copies files when the checksums differ". Are you sure?
> Are checksums that reliable? Can you give me a reference? But I
> agree that GIT uses significantly less space than SVN (and Mercurial
> uses even less). 

GIT computes the MD5SUM of each file and each subdirectory and of the
whole tree. Only subtrees or files which have different MD5SUMs are
every stored, copied or transmitted. Thus creating a copy and checking
it in does almost nothing and takes almost no time to upload.

I know this works because I have switched to GIT for all of my 
personal work. Multiple copies of gcl-2.6.8pre.tgz take no additional
space or time to transmit.

Arch seems to want to trade disk space for file transfer time.
If you check out an arch repository it makes a "pristine copy"
which it caches locally, thus taking twice the disk space. The
advantage is that you don't do any network traffic for some
operations because you have a local, unchanged copy. The disadvantage
is the huge disk space cost. GIT does not store a local copy but only
has to transmit the MD5SUM of the tree root or subdirectory to decide
if changes occur. I'm not sure what SVN does.

You can see it in the numbers I just sent. Arch takes 305M, GIT takes 135M
for the same copy of Axiom.


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