From: Michael J Gruber <git@drmicha.warpmail.net>
To: Junio C Hamano <gitster@pobox.com>
Cc: John Keeping <john@keeping.me.uk>,
Florian Aspart <florian.aspart@gmail.com>,
git@vger.kernel.org
Subject: Re: Using clean/smudge filters with difftool
Date: Sun, 21 Jun 2015 21:29:51 +0200 [thread overview]
Message-ID: <558710AF.9040009@drmicha.warpmail.net> (raw)
In-Reply-To: <xmqqsi9naavw.fsf@gitster.dls.corp.google.com>
Junio C Hamano venit, vidit, dixit 19.06.2015 19:03:
> Michael J Gruber <git@drmicha.warpmail.net> writes:
>
>> Now, since external diff runs on smudged blobs, it appears as if we
>> mixed cleaned and smudged blobs when feeding external diffs; whereas
>> really, we mix "worktree blobs" and "smudged repo blobs", which is okay
>> as per our definition of clean/smudge: the difference is irrelevant by
>> definition.
>
> It does not appear to "mix cleaned and smudged" to me (even though
> before Dscho's commit that John pointed out, we did mix by mistake)
> to me,
... neither to me. I appears as if you missed the past subjunctive ;)
> but you arrived at the correct conclusion in the rest of your
> sentence.
> We treat "worktree files" and "smudged repo blobs" as "comparable"
> because by definition the latter is what you get if you did a
> "checkout" of the blob. Indeed, when we know a worktree file is an
> unmodified checkout from a blob and we want to have a read-only
> temporary file for a "smudged repo blob", we allow that worktree
> file to be used as such.
>
> So in that sense, the commit by Dscho that John pointed out earlier
> was not something that changed the semantics; it merely made things
> consistent (before that commit, we used to use clean version if we
> do not have a usable worktree file).
>
> It is a separate question which of clean or smudged an external diff
> tool should be given to work on.
>
>> I still think that feeding cleaned blobs to external diff would be less
>> surprising (and should be the default, but maybe can't be changed any
>> more) and feeding smudged blobs should be the special case requiring a
>> special config.
>
> Go back six years and make a review comment before 4e218f54 (Smudge
> the files fed to external diff and textconv, 2009-03-21) was taken
> ;-). The argument against that commit may have gone like this:
>
> * The current (that is, current as of 4e218f54^) code is
> inconsistent, and your patch has a side effect of making it
> consistent by always feeding smudged version.
>
> * We however could make it consistent by always feeding clean
> version (i.e. disable borrow-from-working-tree codepath when
> driving external diff). And that gives us cleaner semantics; the
> internal diff and external diff will both work on clean, not
> smudged data.
>
> * Of course, going the "clean" way would not help your cause of
> allowing external diff to work on smudged version, so you would
> need a separate patch on top of that "consistently feed 'clean'
> version" fix to optionally allow "consistently feed 'smudge'
> version" mode to help msysGit issue 177.
>
> And I would have bought such an argument with 97% chance [*1*].
>
> I do not think 6 years have changed things very much with respect to
> the above three-bullet point argument, except that it would be too
> late to set the default to 'clean' all of a sudden. So a plausible
> way forward would be to
>
> * introduce an option to feed 'clean' versions to external diff
> drivers, perhaps with --ext-diff-clean=<driver> command line
> option and GIT_EXTERNAL_DIFF_CLEAN environment variable, both of
> which take precedence over existing --ext-diff/GIT_EXTERNAL_DIFF
>
> * optionally add a configuration variable diff.feedCleanToExternal
> that makes --ext-diff/GIT_EXTERNAL_DIFF behave as if their
> 'clean' siblings were given. Default it to false.
>
> My gut feeling is that textconv should need a similar treatment for
> consistency (after all, it goes through the same prepare_temp_file()
> infrastructure).
>
>
> [Footnote]
>
> *1* The 3% reservation is that I am not entirely convinced that
> "both internal and external get to work on the same 'clean'
> representation gives us cleaner semantics" is always true.
With consistency stepping back behind compatibility, I don't expect any
defaults to change.
But a knob to change defaults would be nice, yes, and in that case for
external diff as well as textconv. A config variable should suffice
given that we have "git -c" these days.
Michael
prev parent reply other threads:[~2015-06-21 19:30 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-16 14:11 Using clean/smudge filters with difftool Florian Aspart
2015-06-18 12:31 ` Michael J Gruber
2015-06-18 13:15 ` Florian Aspart
2015-06-18 13:26 ` John Keeping
2015-06-18 13:51 ` Florian Aspart
2015-06-18 14:11 ` John Keeping
2015-06-18 14:17 ` Florian Aspart
2015-06-18 14:28 ` John Keeping
2015-06-18 15:39 ` Florian Aspart
2015-06-18 16:01 ` John Keeping
2015-06-18 20:00 ` Junio C Hamano
2015-06-18 22:39 ` John Keeping
2015-06-18 22:55 ` Junio C Hamano
2015-06-19 8:57 ` Michael J Gruber
2015-06-19 9:32 ` John Keeping
2015-06-19 15:04 ` Florian Aspart
2015-06-19 17:03 ` Junio C Hamano
2015-06-21 19:29 ` Michael J Gruber [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=558710AF.9040009@drmicha.warpmail.net \
--to=git@drmicha.warpmail.net \
--cc=florian.aspart@gmail.com \
--cc=git@vger.kernel.org \
--cc=gitster@pobox.com \
--cc=john@keeping.me.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.