[PATCH] lockfile: add case insensitive filesystem note

[PATCH] lockfile: add case insensitive filesystem note

[Alan Da Costa via GitGitGadget]

From: Alan Da Costa <alandacosta@gmail.com>

* Add note of case insensitive client filesystems may error due to a lock
  on a case variant ref to more quickly identify failure in fetch/pull

Signed-off-by: Alan Da Costa <alandacosta@gmail.com>
---
    lockfile: add case insensitive filesystem note
    
    When running git fetch or git pull on a case insensitive filesystem
    (e.g., default macOS), if multiple case variants of the same remote ref
    exist (often after a case-only rename), both variant locks map to the
    same on-disk path. When a local update is required, Git creates a lock
    for the first variant and then attempts to lock the second, which
    collides with the same lock file, so an “existing lock” error is
    reported. The underlying issue is mixed-case refs; resolve it by
    consolidating the remote to a single-case variant and update local refs
    accordingly.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2053%2Fadacosta%2Flockfile-add-case-insensitive-filesystem-note-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2053/adacosta/lockfile-add-case-insensitive-filesystem-note-v1
Pull-Request: https://github.com/git/git/pull/2053

 lockfile.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lockfile.c b/lockfile.c
index 1d5ed01682..99a470bd3d 100644
--- a/lockfile.c
+++ b/lockfile.c
@@ -156,7 +156,10 @@ void unable_to_lock_message(const char *path, int err, struct strbuf *buf)
 		    "an editor opened by 'git commit'. Please make sure all processes\n"
 		    "are terminated then try again. If it still fails, a git process\n"
 		    "may have crashed in this repository earlier:\n"
-		    "remove the file manually to continue."),
+		    "remove the file manually to continue.\n\n"
+		    "On case insensitive client filesystems, multiple mixed-case refs will resolve\n"
+		    "to the same lock file, possibly causing this error. If so, ensure your remote\n"
+		    "refs have a single case variant."),
 			    absolute_path(path), strerror(err));
 	} else
 		strbuf_addf(buf, _("Unable to create '%s.lock': %s"),

base-commit: ab427cd991100e94792fce124b0934135abdea4b
-- 
gitgitgadget

Re: [PATCH] lockfile: add case insensitive filesystem note

[Junio C Hamano]

"Alan Da Costa via GitGitGadget" <gitgitgadget@gmail.com> writes:

> From: Alan Da Costa <alandacosta@gmail.com>
>
> * Add note of case insensitive client filesystems may error due to a lock
>   on a case variant ref to more quickly identify failure in fetch/pull

This does not have to be a single-item bulletted list.  Please lose
the leading "* " from the first line, and " " from the second line,
and finish the whole sentence with a full-stop "."

> Signed-off-by: Alan Da Costa <alandacosta@gmail.com>
> ---
>
>     When running git fetch or git pull on a case insensitive filesystem
>     (e.g., default macOS), if multiple case variants of the same remote ref
>     exist (often after a case-only rename), both variant locks map to the
>     same on-disk path. When a local update is required, Git creates a lock
>     for the first variant and then attempts to lock the second, which
>     collides with the same lock file, so an “existing lock” error is
>     reported.

And the message update may help unconfusing the user who gets this
error, which is a good idea.  Thanks for working on this.

>     The underlying issue is mixed-case refs; resolve it by
>     consolidating the remote to a single-case variant and update local refs
>     accordingly.

This does not seem to match anything the patch does, though ;-)

>
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2053%2Fadacosta%2Flockfile-add-case-insensitive-filesystem-note-v1
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2053/adacosta/lockfile-add-case-insensitive-filesystem-note-v1
> Pull-Request: https://github.com/git/git/pull/2053
>
>  lockfile.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)

> diff --git a/lockfile.c b/lockfile.c
> index 1d5ed01682..99a470bd3d 100644
> --- a/lockfile.c
> +++ b/lockfile.c
> @@ -156,7 +156,10 @@ void unable_to_lock_message(const char *path, int err, struct strbuf *buf)
>  		    "an editor opened by 'git commit'. Please make sure all processes\n"
>  		    "are terminated then try again. If it still fails, a git process\n"
>  		    "may have crashed in this repository earlier:\n"
> -		    "remove the file manually to continue."),
> +		    "remove the file manually to continue.\n\n"
> +		    "On case insensitive client filesystems, multiple mixed-case refs will resolve\n"
> +		    "to the same lock file, possibly causing this error. If so, ensure your remote\n"
> +		    "refs have a single case variant."),
>  			    absolute_path(path), strerror(err));

The two lines in the new part of the message seem to be longer than
usual by two words or so.  Can you line wrap to balance?

The error is about our "local" filesystem, isn't it?  If you do not
have control over what the remote does, you have no recourse.  If
using the reftable backend on the local end work around the local
filesystem's case insensitivity, that would be a better suggestion
to give that such a user can actually act on.

In any case, wouldn't it make more sense to do this change
conditionally by looking at the value of the ignore_case global
(which in turn came from the core.ignorecase setting in .git/config
when the repository was created by probing the filesystem
capabilities)?  If you get this error and you are on a case
sensitive system, the additional hints will lead the user to a
wild goose chase.

Thanks.

Re: [PATCH] lockfile: add case insensitive filesystem note

[Patrick Steinhardt]

On Mon, Sep 22, 2025 at 09:54:44PM +0000, Alan Da Costa via GitGitGadget wrote:
> From: Alan Da Costa <alandacosta@gmail.com>
> When running git fetch or git pull on a case insensitive filesystem
> (e.g., default macOS), if multiple case variants of the same remote ref
> exist (often after a case-only rename), both variant locks map to the
> same on-disk path. When a local update is required, Git creates a lock
> for the first variant and then attempts to lock the second, which
> collides with the same lock file, so an “existing lock” error is
> reported. The underlying issue is mixed-case refs; resolve it by
> consolidating the remote to a single-case variant and update local refs
> accordingly.

Are you aware of Karthik's recent patch series at [1]? It looks like
this addresses your exact problem in a more direct way, and the
resulting error messages that we have in that patch series also give a
bit more advice for how to handle the situation.

The patch series wasn't merged yet, but will probably be merged soon.
Could you maybe test that series and say whether it addresses your need?

Thanks!

Patrick

[1]: https://lore.kernel.org/git/20250902-587-git-fetch-1-fails-fetches-on-case-insensitive-repositories-v1-0-35e69bbb507d@gmail.com/

Re: [PATCH] lockfile: add case insensitive filesystem note

[Karthik Nayak]

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Patrick Steinhardt <ps@pks.im> writes:

> On Mon, Sep 22, 2025 at 09:54:44PM +0000, Alan Da Costa via GitGitGadget wrote:
>> From: Alan Da Costa <alandacosta@gmail.com>
>> When running git fetch or git pull on a case insensitive filesystem
>> (e.g., default macOS), if multiple case variants of the same remote ref
>> exist (often after a case-only rename), both variant locks map to the
>> same on-disk path. When a local update is required, Git creates a lock
>> for the first variant and then attempts to lock the second, which
>> collides with the same lock file, so an “existing lock” error is
>> reported. The underlying issue is mixed-case refs; resolve it by
>> consolidating the remote to a single-case variant and update local refs
>> accordingly.
>
> Are you aware of Karthik's recent patch series at [1]? It looks like
> this addresses your exact problem in a more direct way, and the
> resulting error messages that we have in that patch series also give a
> bit more advice for how to handle the situation.
>

Thanks for tagging me.

>
> The patch series wasn't merged yet, but will probably be merged soon.
> Could you maybe test that series and say whether it addresses your need?
>

I agree. This should ideally be fixed with my series. Do let us know if
you test it. My series also has the added advantage that it would
suggest using reftables, wherein, the user can still use
case-conflicting refs in their repository.

> Thanks!
>
> Patrick
>
> [1]: https://lore.kernel.org/git/20250902-587-git-fetch-1-fails-fetches-on-case-insensitive-repositories-v1-0-35e69bbb507d@gmail.com/

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