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Re: special property for text types

From: Branko Čibej <brane_at_xbc.nu>
Date: Sun, 17 Feb 2008 14:43:07 +0100

Kevin Grover wrote:
> Another, more robust solution could be to have an svn:plug-in property
> that would be set to 'text-diff', 'xml-diff', 'winword-diff'. Things
> like text-diff could be configured to standard diff (and XML-diff, if
> present by default, could be the same).

If you do this, then suddenly svn:mime-type becomes completely redundant
-- except for browsing pages straight from the repository, but that
would be better accomplished by hooking into Apache's mime-magic.

And this might not be such a bad thing.

So here's a proposal:

    * Declare svn:mime-type's diff-hint semantics deprecated, to be
      removed in svn-2.0.
    * Introduce, e.g., svn:file-type that serves as a hint to diff;
      offhand, there's text, binary, XML, archive (e.h., tar, zip, jar,
    * Define a reserved namespace for svn:file-type values such that
      custom, application-specific types can be defined in a
      future-proof way.
    * Define a syntax for svn:file-type values so that, e.g., file
      encodings or character sets can be embedded in them.

I envision something like:

standard value: svn:file-type = svn:text:utf-16-le
custom value: svn:file-type = vnd:msword-xml

The downside of this proposal is that it reinvents the wheel, since MIME
already supports all that.

The alternative would be to introduce full MIME content-type and
content-transfer-encoding semantics; however, that would require some
serious UI work to create simple shortcuts for the most often used
combination. I suspect users would be much happier if they could say, e.g.,

    svn ps svn:file-type text:uft-8

rather than

    svn ps svn:content-type "text/plain; charset=UTF-8"
    svn ps svn:content-transfer-encoding binary

On the other hand, MIME is tailored for e-mail, not general text; hence,
for example, you can't use "Content-Transfer-Encoding: 8bit" for any
UTF-8 file, because that assumes CRLF line endings and sets an upper
bound to line length.

This whole fubar isn't all that trivial to solve. :)

-- Brane

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Received on 2008-02-17 14:44:02 CET

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