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Re: Subtree mergeinfo -- what I learnt at the Hackathon

From: Johan Corveleyn <jcorvel_at_gmail.com>
Date: Wed, 11 Jul 2012 13:28:29 +0200

On Wed, Jul 11, 2012 at 6:19 AM, Branko Čibej <brane_at_wandisco.com> wrote:
> On 10.07.2012 23:40, Julian Foad wrote:
>> I think the essence of this line of thought is:
>> We set up all of the possible mergeinfo scenarios, and we see what 'merge' does, and we see what 1.7 'merge --reintegrate' does, and we debate what cases are 'supported' versus knowingly 'unsupported', and we see what an ideal symmetric merge would do. Then we evaluate the current 'symmetric'[1] implementation against that: does it do "the same as" or "better than" or "worse than" what a user can do with the existing merge (assuming he/she chooses the "reintegrate" option appropriately).
>> It's not easy to set up all of the possible scenarios: reintegrating the root but excluding a subtree, for example, can't be done in a single merge command. Does that mean that scenario is uninteresting? No, I don't think so. What we can do is eliminate the existing merge command from the set-up phases of the test scenarios, and set up the desired mergeinfo directly: "faking it", if you will. Doing it that way separates the concerns: the question of what the merge command will do, given a certain scenario, is a separate question from how we can use merges to create that scenario.
>> The question I have at the moment is: Does this approach to evaluation make sense to you?
> Am I correct in assuming that most of this discussion is a consequence
> of the current implementation of mergeinfo inheritance? I.e., that there
> are a certain number of hoops one needs to jump through in order to
> determine which, if any, mergeinfo applies to a particular file (or
> subtree)?
> Assuming that retrieving merginfo is expensive (which I gather it is
> right now) and you want to minimize the number of explicit mergeinfo
> lookups, your approach makes sense to me.

I assume Julian's remarks are not related to "expensiveness of
retrieving mergeinfo", but to the difficulty of *creating* certain
mergeinfo situations (difficult to create through normal UI commands),
although these configurations are still interesting to have as a test
fixture (and the merge logic should be able to handle them in a sane
way -- and we should be able to specify what the behavior should be).

+1, I'd say.

Perhaps we should have both:

- Tests with artificially created mergeinfo (a bit like "unit tests":
we give the merge algorithm some input, and expect certain output; we
don't care about how a user would create that input -- also a bit
comparable to "synthetic benchmarks").

- Tests with a full scenario of user commands (a bit like "integration
tests": we consider the entire application, and treat it like a black
box; we only interact with actual user commands -- a bit comparable to
"real-world benchmarks").

BTW, great effort, Julian, in trying to categorize these scenarios a
bit, and trying to describe the current and desired behaviors, in a
rather concise manner. I agree this is the best way forward right now

Received on 2012-07-11 13:29:27 CEST

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