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From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: Han-Wen Nienhuys via GitGitGadget <gitgitgadget@gmail.com>
Cc: git@vger.kernel.org, Han-Wen Nienhuys <hanwenn@gmail.com>,
	Han-Wen Nienhuys <hanwen@google.com>
Subject: Re: [PATCH v3 2/3] Modify pseudo refs through ref backend storage
Date: Fri, 17 Jul 2020 10:52:06 +0200 (CEST)	[thread overview]
Message-ID: <nycvar.QRO.7.76.6.2007171042461.54@tvgsbejvaqbjf.bet> (raw)
In-Reply-To: <79cd5dd480a4218d4563120c03046375594cc23e.1594925141.git.gitgitgadget@gmail.com>

Hi Han-Wen,

On Thu, 16 Jul 2020, Han-Wen Nienhuys via GitGitGadget wrote:

> From: Han-Wen Nienhuys <hanwen@google.com>
>
> The previous behavior was introduced in commit 74ec19d4be
> ("pseudorefs: create and use pseudoref update and delete functions",
> Jul 31, 2015), with the justification "alternate ref backends still
> need to store pseudorefs in GIT_DIR".
>
> Refs such as REBASE_HEAD are read through the ref backend. This can
> only work consistently if they are written through the ref backend as
> well. Tooling that works directly on files under .git should be
> updated to use git commands to read refs instead.
>
> The following behaviors change:
>
> * Updates to pseudorefs (eg. ORIG_HEAD) with
>   core.logAllRefUpdates=always will create reflogs for the pseudoref.
>
> * non-HEAD pseudoref symrefs are also dereferenced on deletion. Update
>   t1405 accordingly.

Unfortunately, there is still a breakage in t1405, although it only really
shows up on Windows and macOS because of case-insensitive filesystems.
https://github.com/gitgitgadget/git/runs/879772942?check_suite_focus=true
shows the concrete problem: t1405.17 'delete_ref(refs/heads/foo)' will
fail thusly:

	++ test-tool ref-store main delete-ref msg refs/heads/foo c90e4dc5e12224a428dedfbd45ba11e5531706a2 0
	error: cannot lock ref 'refs/heads/foo': is at 1e995a94b5a60488b6ebaf78ec779d85a55ea700 but expected c90e4dc5e12224a428dedfbd45ba11e5531706a2
	error: last command exited with $?=1

The reason is that there exists a `refs/heads/foo` _and_ the symref `FOO`
(which points to `refs/heads/master`, which is at 1e995a).

An earlier symptom of this bug is visible on Linux, too, though: when
you run t1405.4 'delete_refs(FOO, refs/tags/new-tag)', it shows this:

	+ git rev-parse FOO --
	warning: ignoring dangling symref FOO
	fatal: bad revision 'FOO'

(Seeing this warning suggests to me that this should probably be caught
_by the regression test_, i.e. stderr should be redirected, and it should
be verified via `test_i18ngrep` that that warning is not shown.)

The reason for this warning is that the symref `.git/FOO` is no longer
removed as part of t1405.4 'delete_refs(FOO, refs/tags/new-tag)'. I've
used this patch to bisect the breakage down to this here patch:

-- snip --
diff --git a/t/t1405-main-ref-store.sh b/t/t1405-main-ref-store.sh
index a8d695cd4f1..779906d607f 100755
--- a/t/t1405-main-ref-store.sh
+++ b/t/t1405-main-ref-store.sh
@@ -34,6 +34,7 @@ test_expect_success 'delete_refs(FOO, refs/tags/new-tag)' '
 	m=$(git rev-parse master) &&
 	$RUN delete-refs 0 nothing FOO refs/tags/new-tag &&
 	test_must_fail git rev-parse FOO -- &&
+	test_path_is_missing .git/FOO &&
 	test_must_fail git rev-parse refs/tags/new-tag --&&
 	test_must_fail git rev-parse master -- &&
 	git update-ref refs/heads/master $m
-- snap --

Hopefully you can figure out what is going wrong.

Ciao,
Dscho

  reply	other threads:[~2020-07-17 10:18 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-06 17:29 [PATCH 0/2] Remove special casing for PSEUDOREF updates Han-Wen Nienhuys via GitGitGadget
2020-07-06 17:29 ` [PATCH 1/2] Modify pseudo refs through ref backend storage Han-Wen Nienhuys via GitGitGadget
2020-07-06 20:26   ` Junio C Hamano
2020-07-07 13:56     ` Han-Wen Nienhuys
2020-07-07 15:20       ` Junio C Hamano
2020-07-07 17:15         ` Han-Wen Nienhuys
2020-07-07 18:14           ` Junio C Hamano
2020-07-06 17:29 ` [PATCH 2/2] Make HEAD a PSEUDOREF rather than PER_WORKTREE Han-Wen Nienhuys via GitGitGadget
2020-07-06 20:30   ` Junio C Hamano
2020-07-07  9:24     ` Han-Wen Nienhuys
2020-07-09 21:11 ` [PATCH v2 0/3] Remove special casing for PSEUDOREF updates Han-Wen Nienhuys via GitGitGadget
2020-07-09 21:11   ` [PATCH v2 1/3] t1400: use git rev-parse for testing PSEUDOREF existence Han-Wen Nienhuys via GitGitGadget
2020-07-09 21:11   ` [PATCH v2 2/3] Modify pseudo refs through ref backend storage Han-Wen Nienhuys via GitGitGadget
2020-07-09 21:11   ` [PATCH v2 3/3] Make HEAD a PSEUDOREF rather than PER_WORKTREE Han-Wen Nienhuys via GitGitGadget
2020-07-10 19:25   ` [PATCH v2 0/3] Remove special casing for PSEUDOREF updates Junio C Hamano
2020-07-16 18:45   ` [PATCH v3 " Han-Wen Nienhuys via GitGitGadget
2020-07-16 18:45     ` [PATCH v3 1/3] t1400: use git rev-parse for testing PSEUDOREF existence Han-Wen Nienhuys via GitGitGadget
2020-07-16 18:45     ` [PATCH v3 2/3] Modify pseudo refs through ref backend storage Han-Wen Nienhuys via GitGitGadget
2020-07-17  8:52       ` Johannes Schindelin [this message]
2020-07-27 15:41         ` Han-Wen Nienhuys
2020-07-16 18:45     ` [PATCH v3 3/3] Make HEAD a PSEUDOREF rather than PER_WORKTREE Han-Wen Nienhuys via GitGitGadget
2020-07-16 22:09     ` [PATCH v3 0/3] Remove special casing for PSEUDOREF updates Junio C Hamano
2020-07-27  8:50       ` Han-Wen Nienhuys
2020-07-27 16:20         ` Junio C Hamano
2020-08-03 19:07           ` Han-Wen Nienhuys
2020-08-03 20:07             ` Junio C Hamano
2020-08-05  1:45               ` Junio C Hamano
2020-08-05 10:48                 ` Han-Wen Nienhuys
2020-08-05 15:54                   ` Junio C Hamano
2020-08-10 14:27                     ` Han-Wen Nienhuys
2020-08-10 16:04                       ` Junio C Hamano
2020-08-11 10:49                         ` Han-Wen Nienhuys
2020-08-11 18:38                           ` Junio C Hamano
2020-08-19 13:19                     ` Han-Wen Nienhuys
2020-08-19 15:52                       ` Junio C Hamano
2020-07-27 16:25     ` [PATCH v4 " Han-Wen Nienhuys via GitGitGadget
2020-07-27 16:25       ` [PATCH v4 1/3] t1400: use git rev-parse for testing PSEUDOREF existence Han-Wen Nienhuys via GitGitGadget
2020-07-27 16:25       ` [PATCH v4 2/3] Modify pseudo refs through ref backend storage Han-Wen Nienhuys via GitGitGadget
2020-07-27 16:25       ` [PATCH v4 3/3] Make HEAD a PSEUDOREF rather than PER_WORKTREE Han-Wen Nienhuys via GitGitGadget

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