Re: standalone library/tool to query commit-graph?

From: Jakub Narebski <jnareb@gmail.com>
Date: Jun 25, 2019, 18:27 UTC
Message-ID: <86ftnx4j1n.fsf@gmail.com>
In-Reply-To: <87o93sfahj.fsf@evledraar.gmail.com>

Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes: [...]

Show 9 quoted lines

> To clarify (and I should have said) I meant it'll include only packed
> commits in the mode Karl Ostmo invoked it in, as Derrick points out.
>
> But yeah, you can of course give it arbitrary starting points, but
> needing to deal with those sorts of caveats makes it rather useless in
> practice for the sort of use-case Jakub mused about, but more
> importantly a full XML dump of the graph isn't going to get much of a
> benefit from the commit graph, it helps with algorithms that want to
> avoid those sorts of full walks.

Actually for an "XML dump" of a graph of revisions (assuming that you can give nodes and edges in arbitrary order in this graph output format) doing it using serialized commit-graph should be faster: you only need to read one file, and convert it to other format (perhaps even in a streaming manner). No need to delta-unpack, decompress and parse commit objects.

Though on the other hand you are right: if "git log --graph" uses serialized commit graph, and it is used for XML / JSON dump, it should also be fast. If there is no serialized commit graph, you still can generate XML dump.

Best, -- Jakub Narębski