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From: Jeff King <peff@peff.net>
To: Elijah Newren <newren@gmail.com>
Cc: git@vger.kernel.org, larsxschneider@gmail.com,
	sandals@crustytoothpaste.net, me@ttaylorr.com,
	jrnieder@gmail.com
Subject: Re: [PATCH 09/10] fast-export: add a --show-original-ids option to show original names
Date: Sun, 11 Nov 2018 02:20:07 -0500
Message-ID: <20181111072007.GI30850@sigill.intra.peff.net> (raw)
In-Reply-To: <20181111062312.16342-10-newren@gmail.com>

On Sat, Nov 10, 2018 at 10:23:11PM -0800, Elijah Newren wrote:

> Knowing the original names (hashes) of commits, blobs, and tags can
> sometimes enable post-filtering that would otherwise be difficult or
> impossible.  In particular, the desire to rewrite commit messages which
> refer to other prior commits (on top of whatever other filtering is
> being done) is very difficult without knowing the original names of each
> commit.
> 
> This commit teaches a new --show-original-ids option to fast-export
> which will make it add a 'originally <hash>' line to blob, commits, and
> tags.  It also teaches fast-import to parse (and ignore) such lines.

Makes sense as a feature; I think filter-branch can make its mappings
available, too.

Do we need to worry about compatibility with other fast-import programs?
I think no, because this is not enabled by default (so if sending the
extra lines to another importer hurts, the answer is "don't do that").

I have a vague feeling that there might be some way to combine this with
--export-marks or --no-data, but I can't really think of a way. They
seem related, but not quite.

> ---
>  Documentation/git-fast-export.txt |  7 +++++++
>  builtin/fast-export.c             | 20 +++++++++++++++-----
>  fast-import.c                     | 17 +++++++++++++++++
>  t/t9350-fast-export.sh            | 17 +++++++++++++++++
>  4 files changed, 56 insertions(+), 5 deletions(-)

The fast-import format is documented in Documentation/git-fast-import.txt.
It might need an update to cover the new format.

> --- a/Documentation/git-fast-export.txt
> +++ b/Documentation/git-fast-export.txt
> @@ -121,6 +121,13 @@ marks the same across runs.
>  	used by a repository which already contains the necessary
>  	parent commits.
>  
> +--show-original-ids::
> +	Add an extra directive to the output for commits and blobs,
> +	`originally <SHA1SUM>`.  While such directives will likely be
> +	ignored by importers such as git-fast-import, it may be useful
> +	for intermediary filters (e.g. for rewriting commit messages
> +	which refer to older commits, or for stripping blobs by id).

I'm not quite sure how a blob ends up being rewritten by fast-export (I
get that commits may change due to dropping parents).

The name "originally" doesn't seem great to me. Probably because I would
continually wonder if it has one "l" or two. ;) Perhaps something like
"original-oid" might be better. That's well into bikeshed territory,
though.

-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
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 [this message]
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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