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From: Jeff King <peff@peff.net>
To: Elijah Newren <newren@gmail.com>
Cc: Git Mailing List <git@vger.kernel.org>,
	Lars Schneider <larsxschneider@gmail.com>,
	"brian m. carlson" <sandals@crustytoothpaste.net>,
	Taylor Blau <me@ttaylorr.com>,
	Jonathan Nieder <jrnieder@gmail.com>
Subject: Re: [PATCH 06/10] fast-export: when using paths, avoid corrupt stream with non-existent mark
Date: Mon, 12 Nov 2018 07:45:47 -0500
Message-ID: <20181112124547.GG3956@sigill.intra.peff.net> (raw)
In-Reply-To: <CABPp-BGF8C5vhyVbAwpmXeii452fBgtvL4dPRLWdOPxLiCYR0A@mail.gmail.com>

On Sun, Nov 11, 2018 at 12:01:43AM -0800, Elijah Newren wrote:

> > It does seem funny that the behavior for the earlier case (bounded
> > commits) and this case (skipping some commits) are different. Would you
> > ever want to keep walking backwards to find an ancestor in the earlier
> > case? Or vice versa, would you ever want to simply delete a tag in a
> > case like this one?
> >
> > I'm not sure sure, but I suspect you may have thought about it a lot
> > harder than I have. :)
> 
> I'm not sure why you thought the behavior for the two cases was
> different?  For both patches, my testcases used path limiting; it was
> you who suggested employing a negative revision to bound the commits.

Sorry, I think I just got confused. I was thinking about the
documentation fixup you started with, which did regard bounded commits.
But that's not relevant here.

> Anyway, for both patches assuming you haven't bounded the commits, you
> can attempt to keep walking backwards to find an earlier ancestor, but
> the fundamental fact is you aren't guaranteed that you can find one
> (i.e. some tag or branch points to a commit that didn't modify any of
> the specified paths, and nor did any of its ancestors back to any root
> commits).  I hit that case lots of times.  If the user explicitly
> requested a tag or branch for export (and requested tag rewriting),
> and limited to certain paths that had never existed in the repository
> as of the time of the tag or branch, then you hit the cases these
> patches worry about.  Patch 4 was about (annotated and signed) tags,
> this patch is about unannotated tags and branches and other refs.

OK, that makes more sense.

So I guess my question is: in patch 4, why do we not walk back to find
an appropriate ancestor pointed to by the signed tag object, as we do
here for the unannotated case?

And I think the answer is: we already do that. It's just that the
unannotated case never learned the same trick. So basically it's:

  1. rewriting annotated tags to ancestors is already known on "master"

  2. patch 4 further teaches it to drop a tag when that fails

  3. patch 6 teaches both (1) and (2) to the unannotated code path,
     which knew neither

Is that right?

> > This hunk makes sense.
> 
> Cool, this was the entirety of the code...so does this mean that the
> code makes more sense than my commit message summary did?  ...and
> perhaps that my attempts to answer your questions in this email
> weren't necessary anymore?

No, it only made sense that the hunk implemented what you claimed in the
commit message. ;)

I think your responses did help me understand that what the commit
message is claiming is a good thing.

-Peff

  reply index

Thread overview: 90+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-23 13:04 Import/Export as a fast way to purge files from Git? Lars Schneider
2018-09-23 14:55 ` Eric Sunshine
2018-09-23 15:58   ` Lars Schneider
2018-09-23 15:53 ` brian m. carlson
2018-09-23 17:04   ` Jeff King
2018-09-24 17:24 ` Elijah Newren
2018-10-31 19:15   ` Lars Schneider
2018-11-01  7:12     ` Elijah Newren
2018-11-11  6:23       ` [PATCH 00/10] fast export and import fixes and features Elijah Newren
2018-11-11  6:23         ` [PATCH 01/10] git-fast-import.txt: fix documentation for --quiet option Elijah Newren
2018-11-11  6:33           ` Jeff King
2018-11-11  6:23         ` [PATCH 02/10] git-fast-export.txt: clarify misleading documentation about rev-list args Elijah Newren
2018-11-11  6:36           ` Jeff King
2018-11-11  7:17             ` Elijah Newren
2018-11-13 23:25               ` Elijah Newren
2018-11-13 23:39                 ` Jonathan Nieder
2018-11-14  0:02                   ` Elijah Newren
2018-11-11  6:23         ` [PATCH 03/10] fast-export: use value from correct enum Elijah Newren
2018-11-11  6:36           ` Jeff King
2018-11-11 20:10             ` Ævar Arnfjörð Bjarmason
2018-11-12  9:12               ` Ævar Arnfjörð Bjarmason
2018-11-12 11:31               ` Jeff King
2018-11-11  6:23         ` [PATCH 04/10] fast-export: avoid dying when filtering by paths and old tags exist Elijah Newren
2018-11-11  6:44           ` Jeff King
2018-11-11  7:38             ` Elijah Newren
2018-11-12 12:32               ` Jeff King
2018-11-12 22:50             ` brian m. carlson
2018-11-13 14:38               ` Jeff King
2018-11-11  6:23         ` [PATCH 05/10] fast-export: move commit rewriting logic into a function for reuse Elijah Newren
2018-11-11  6:47           ` Jeff King
2018-11-11  6:23         ` [PATCH 06/10] fast-export: when using paths, avoid corrupt stream with non-existent mark Elijah Newren
2018-11-11  6:53           ` Jeff King
2018-11-11  8:01             ` Elijah Newren
2018-11-12 12:45               ` Jeff King [this message]
2018-11-12 15:36                 ` Elijah Newren
2018-11-11  6:23         ` [PATCH 07/10] fast-export: ensure we export requested refs Elijah Newren
2018-11-11  7:02           ` Jeff King
2018-11-11  8:20             ` Elijah Newren
2018-11-11  6:23         ` [PATCH 08/10] fast-export: add --reference-excluded-parents option Elijah Newren
2018-11-11  7:11           ` Jeff King
2018-11-11  6:23         ` [PATCH 09/10] fast-export: add a --show-original-ids option to show original names Elijah Newren
2018-11-11  7:20           ` Jeff King
2018-11-11  8:32             ` Elijah Newren
2018-11-12 12:53               ` Jeff King
2018-11-12 15:46                 ` Elijah Newren
2018-11-12 16:31                   ` Jeff King
2018-11-11  6:23         ` [PATCH 10/10] fast-export: add --always-show-modify-after-rename Elijah Newren
2018-11-11  7:23           ` Jeff King
2018-11-11  8:42             ` Elijah Newren
2018-11-12 12:58               ` Jeff King
2018-11-12 18:08                 ` Elijah Newren
2018-11-13 14:45                   ` Jeff King
2018-11-13 17:10                     ` Elijah Newren
2018-11-14  7:14                       ` Jeff King
2018-11-11  7:27         ` [PATCH 00/10] fast export and import fixes and features Jeff King
2018-11-11  8:44           ` Elijah Newren
2018-11-12 13:00             ` Jeff King
2018-11-14  0:25         ` [PATCH v2 00/11] " Elijah Newren
2018-11-14  0:25           ` [PATCH v2 01/11] git-fast-import.txt: fix documentation for --quiet option Elijah Newren
2018-11-14  0:25           ` [PATCH v2 02/11] git-fast-export.txt: clarify misleading documentation about rev-list args Elijah Newren
2018-11-14  0:25           ` [PATCH v2 03/11] fast-export: use value from correct enum Elijah Newren
2018-11-14  0:25           ` [PATCH v2 04/11] fast-export: avoid dying when filtering by paths and old tags exist Elijah Newren
2018-11-14 19:17             ` SZEDER Gábor
2018-11-14 23:13               ` Elijah Newren
2018-11-14  0:25           ` [PATCH v2 05/11] fast-export: move commit rewriting logic into a function for reuse Elijah Newren
2018-11-14  0:25           ` [PATCH v2 06/11] fast-export: when using paths, avoid corrupt stream with non-existent mark Elijah Newren
2018-11-14  0:25           ` [PATCH v2 07/11] fast-export: ensure we export requested refs Elijah Newren
2018-11-14  0:25           ` [PATCH v2 08/11] fast-export: add --reference-excluded-parents option Elijah Newren
2018-11-14 19:27             ` SZEDER Gábor
2018-11-14 23:16               ` Elijah Newren
2018-11-14  0:25           ` [PATCH v2 09/11] fast-import: remove unmaintained duplicate documentation Elijah Newren
2018-11-14  0:25           ` [PATCH v2 10/11] fast-export: add a --show-original-ids option to show original names Elijah Newren
2018-11-14  0:26           ` [PATCH v2 11/11] fast-export: add --always-show-modify-after-rename Elijah Newren
2018-11-14  7:25           ` [PATCH v2 00/11] fast export and import fixes and features Jeff King
2018-11-16  7:59           ` [PATCH v3 " Elijah Newren
2018-11-16  7:59             ` [PATCH v3 01/11] fast-export: convert sha1 to oid Elijah Newren
2018-11-16  7:59             ` [PATCH v3 02/11] git-fast-import.txt: fix documentation for --quiet option Elijah Newren
2018-11-16  7:59             ` [PATCH v3 03/11] git-fast-export.txt: clarify misleading documentation about rev-list args Elijah Newren
2018-11-16  7:59             ` [PATCH v3 04/11] fast-export: use value from correct enum Elijah Newren
2018-11-16  7:59             ` [PATCH v3 05/11] fast-export: avoid dying when filtering by paths and old tags exist Elijah Newren
2018-11-16  7:59             ` [PATCH v3 06/11] fast-export: move commit rewriting logic into a function for reuse Elijah Newren
2018-11-16  7:59             ` [PATCH v3 07/11] fast-export: when using paths, avoid corrupt stream with non-existent mark Elijah Newren
2018-11-16  7:59             ` [PATCH v3 08/11] fast-export: ensure we export requested refs Elijah Newren
2018-11-16  7:59             ` [PATCH v3 09/11] fast-export: add --reference-excluded-parents option Elijah Newren
2018-11-16  7:59             ` [PATCH v3 10/11] fast-import: remove unmaintained duplicate documentation Elijah Newren
2018-11-16  7:59             ` [PATCH v3 11/11] fast-export: add a --show-original-ids option to show original names Elijah Newren
2018-11-16 12:29               ` SZEDER Gábor
2018-11-16  8:50             ` [PATCH v3 00/11] fast export and import fixes and features Jeff King
2018-11-12  9:17       ` Import/Export as a fast way to purge files from Git? Ævar Arnfjörð Bjarmason
2018-11-12 15:34         ` Elijah Newren

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