Re: [PATCH 4/5] fast-export: Introduce --inline-blobs

From: Jonathan Nieder <jrnieder@gmail.com>
Date: Jan 19, 2011, 21:48 UTC
Message-ID: <20110119214827.GA31733@burratino>
In-Reply-To: <7vtyh4smer.fsf@alter.siamese.dyndns.org>

Junio C Hamano wrote:

> Ramkumar Ramachandra <artagnon@gmail.com> writes:

>> Introduce a new command-line option --inline-blobs that always inlines
>> blobs instead of referring to them via marks or their original SHA-1
>> hash.

[...]

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> Hmm, this smells somewhat fishy.
>
> Wasn't G-F-I designed to be a common stream format for other SCMs to
> generate streams, so that importers and exporters can be written once for
> each SCM to interoperate?

Here is one way to sell it:

	With the inline blobs feature, fast-import backends have to
	maintain less state.  Using it should speed up exporting.

	This is made optional because ...

I haven't thought through whether it ought to be optional or measured the effect on import performance.

A separate question is what an svn fast-import backend should do with all those blobs that are not ready to be written to dump. As a hack while prototyping, one can rely on the "current" fast-export output, even though that is not flexible or futureproof. Longer term, the folllowing sounds very interesting

> Just thinking aloud, but is it possible to write a filter that converts an
> arbitrary G-F-I stream with referenced blobs into a G-F-I stream without
> referenced blobs by inlining all the blobs?

to avoid complexity in the svn fast-import backend itself. (Complicating detail: such a filter would presumably take responsibility for --export-marks, so it might want a way to retrieve commit marks from its downstream.)