[PATCH] docs: note that extensions.compatobjectformat is experimental

[PATCH] docs: note that extensions.compatobjectformat is experimental

[brian m. carlson]

The compatibility object format is only implemented for loose objects,
not packed objects, so anyone attempting to push or fetch data into a
repository with this option will likely not see it work as expected.  In
addition, the underlying storage of loose object mapping is likely to
change because the current format is inefficient and does not handle
important mapping information such as that of submodules.

It would have been preferable to initially document that this was an
experimental feature, but we did not do so.  We hinted at the fact that
this functionality is incomplete in the description, but did not say so
explicitly.  Let's do so now: indicate that this feature is
experimental, incomplete, and subject to change.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
---
This was spurred by the fact that I saw Gitolite had added SHA-256
support and then that users were expecting extensions.compatobjectformat
to work, when it clearly does not (and, in fact, in some cases breaks
pushing into the repository).

I know that some people will not appreciate this feature being
retroactively marked as experimental, but it is definitively broken for
real-world use cases without the rest of my sha256-interop branch.
Technically someone could always insert loose objects and then pack
them, and because the old loose object mapping was present, the mapping
would work, but, as mentioned, this would perform pathologically with
even small repositories, so it's not a useful configuration.

 Documentation/config/extensions.adoc | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Documentation/config/extensions.adoc b/Documentation/config/extensions.adoc
index 9e2f321a6d..292e95ddae 100644
--- a/Documentation/config/extensions.adoc
+++ b/Documentation/config/extensions.adoc
@@ -14,6 +14,9 @@ compatObjectFormat::
 	compatObjectFormat.  As well as being able to use oids encoded in
 	compatObjectFormat in addition to oids encoded with objectFormat to
 	locally specify objects.
++
+Note that the functionality enabled by this option is experimental, incomplete,
+and subject to change.
 
 noop::
 	This extension does not change git's behavior at all. It is useful only

Re: [PATCH] docs: note that extensions.compatobjectformat is experimental

[Junio C Hamano]

"brian m. carlson" <sandals@crustytoothpaste.net> writes:

> The compatibility object format is only implemented for loose objects,
> not packed objects, so anyone attempting to push or fetch data into a
> repository with this option will likely not see it work as expected.  In
> addition, the underlying storage of loose object mapping is likely to
> change because the current format is inefficient and does not handle
> important mapping information such as that of submodules.

It is "experimental" in the sense that a developer who is interested
in making the feature work end-to-end for the first time can use the
code behind the flag to prepare loose objects to prepare what is to
be transferred; it sounds more like this one is "not working yet" ...

> diff --git a/Documentation/config/extensions.adoc b/Documentation/config/extensions.adoc
> index 9e2f321a6d..292e95ddae 100644
> --- a/Documentation/config/extensions.adoc
> +++ b/Documentation/config/extensions.adoc
> @@ -14,6 +14,9 @@ compatObjectFormat::
>  	compatObjectFormat.  As well as being able to use oids encoded in
>  	compatObjectFormat in addition to oids encoded with objectFormat to
>  	locally specify objects.
> ++
> +Note that the functionality enabled by this option is experimental, incomplete,
> +and subject to change.

... as the only end-user-perceivable purpose the compat format
serves is to exchange data between two repositories that use
different hash functions, no?

The word "experimental" to me implies that it at least lets you
complete a minimum end-user journey of the feature end-to-end.

There are different degree of experimental in this project and we
may want to do something about it, but in any case this is a welcome
change in the right direction to steer those with mere curiosity
away from hurting themselves.

    Note that the functionality hidden behind this extension is
    incomplete and the extension exists solely to allow us to
    continue developping it further.

might give them a stronger discouragement?

>  noop::
>  	This extension does not change git's behavior at all. It is useful only

Re: [PATCH] docs: note that extensions.compatobjectformat is experimental

[brian m. carlson]

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On 2025-08-25 at 17:25:57, Junio C Hamano wrote:
> "brian m. carlson" <sandals@crustytoothpaste.net> writes:
> 
> > The compatibility object format is only implemented for loose objects,
> > not packed objects, so anyone attempting to push or fetch data into a
> > repository with this option will likely not see it work as expected.  In
> > addition, the underlying storage of loose object mapping is likely to
> > change because the current format is inefficient and does not handle
> > important mapping information such as that of submodules.
> 
> It is "experimental" in the sense that a developer who is interested
> in making the feature work end-to-end for the first time can use the
> code behind the flag to prepare loose objects to prepare what is to
> be transferred; it sounds more like this one is "not working yet" ...
> 
> > diff --git a/Documentation/config/extensions.adoc b/Documentation/config/extensions.adoc
> > index 9e2f321a6d..292e95ddae 100644
> > --- a/Documentation/config/extensions.adoc
> > +++ b/Documentation/config/extensions.adoc
> > @@ -14,6 +14,9 @@ compatObjectFormat::
> >  	compatObjectFormat.  As well as being able to use oids encoded in
> >  	compatObjectFormat in addition to oids encoded with objectFormat to
> >  	locally specify objects.
> > ++
> > +Note that the functionality enabled by this option is experimental, incomplete,
> > +and subject to change.
> 
> ... as the only end-user-perceivable purpose the compat format
> serves is to exchange data between two repositories that use
> different hash functions, no?

It works if you want to do `git rev-parse --output-object-format=sha1
<some-sha256-oid>` (or the reverse) and all of your objects entered the
repository as loose objects.  Otherwise, it isn't very useful.

It definitely does not currently let you exchange data between two
repositories that use different hash functions unless you use my
in-progress branch.

The eventual goal is to let people do something like `git rev-parse
foobar^{sha1}` as well as interoperate with other repositories.  Neither
of those are currently in place.

> The word "experimental" to me implies that it at least lets you
> complete a minimum end-user journey of the feature end-to-end.

I definitely don't think that's what it does.  It has extremely limited
useful functionality, pretty much entirely confined to rev-parse.

> There are different degree of experimental in this project and we
> may want to do something about it, but in any case this is a welcome
> change in the right direction to steer those with mere curiosity
> away from hurting themselves.
> 
>     Note that the functionality hidden behind this extension is
>     incomplete and the extension exists solely to allow us to
>     continue developping it further.
> 
> might give them a stronger discouragement?

I'll re-roll with something like that in v2.
-- 
brian m. carlson (they/them)
Toronto, Ontario, CA

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[PATCH v2] docs: note that extensions.compatobjectformat is incomplete

[brian m. carlson]

The compatibility object format is only implemented for loose objects,
not packed objects, so anyone attempting to push or fetch data into a
repository with this option will likely not see it work as expected.  In
addition, the underlying storage of loose object mapping is likely to
change because the current format is inefficient and does not handle
important mapping information such as that of submodules.

It would have been preferable to initially document that this was not
yet ready for prime time, but we did not do so.  We hinted at the fact
that this functionality is incomplete in the description, but did not
say so explicitly.  Let's do so now: indicate that this feature is
incomplete and subject to change and that the option is not designed to
be used by end users.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
---
 Documentation/config/extensions.adoc | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/config/extensions.adoc b/Documentation/config/extensions.adoc
index 9e2f321a6d..df448da813 100644
--- a/Documentation/config/extensions.adoc
+++ b/Documentation/config/extensions.adoc
@@ -14,6 +14,10 @@ compatObjectFormat::
 	compatObjectFormat.  As well as being able to use oids encoded in
 	compatObjectFormat in addition to oids encoded with objectFormat to
 	locally specify objects.
++
+Note that the functionality enabled by this option is incomplete and subject to
+change.  This option currently exists only to allow development and testing of
+the underlying feature and is not designed to be enabled by end users.
 
 noop::
 	This extension does not change git's behavior at all. It is useful only

Re: [PATCH v2] docs: note that extensions.compatobjectformat is incomplete

[Junio C Hamano]

"brian m. carlson" <sandals@crustytoothpaste.net> writes:

> diff --git a/Documentation/config/extensions.adoc b/Documentation/config/extensions.adoc
> index 9e2f321a6d..df448da813 100644
> --- a/Documentation/config/extensions.adoc
> +++ b/Documentation/config/extensions.adoc
> @@ -14,6 +14,10 @@ compatObjectFormat::
>  	compatObjectFormat.  As well as being able to use oids encoded in
>  	compatObjectFormat in addition to oids encoded with objectFormat to
>  	locally specify objects.
> ++
> +Note that the functionality enabled by this option is incomplete and subject to
> +change.  This option currently exists only to allow development and testing of
> +the underlying feature and is not designed to be enabled by end users.

Much better.  Let's further do "This option" -> "This extension", as
all the others described in this document call themselves as such.

Thanks.

[PATCH v3] docs: note that extensions.compatobjectformat is incomplete

[brian m. carlson]

The compatibility object format is only implemented for loose objects,
not packed objects, so anyone attempting to push or fetch data into a
repository with this option will likely not see it work as expected.  In
addition, the underlying storage of loose object mapping is likely to
change because the current format is inefficient and does not handle
important mapping information such as that of submodules.

It would have been preferable to initially document that this was not
yet ready for prime time, but we did not do so.  We hinted at the fact
that this functionality is incomplete in the description, but did not
say so explicitly.  Let's do so now: indicate that this feature is
incomplete and subject to change and that the option is not designed to
be used by end users.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
---
 Documentation/config/extensions.adoc | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/config/extensions.adoc b/Documentation/config/extensions.adoc
index 9e2f321a6d..9d50a3501e 100644
--- a/Documentation/config/extensions.adoc
+++ b/Documentation/config/extensions.adoc
@@ -14,6 +14,10 @@ compatObjectFormat::
 	compatObjectFormat.  As well as being able to use oids encoded in
 	compatObjectFormat in addition to oids encoded with objectFormat to
 	locally specify objects.
++
+Note that the functionality enabled by this option is incomplete and subject to
+change.  This extension currently exists only to allow development and testing of
+the underlying feature and is not designed to be enabled by end users.
 
 noop::
 	This extension does not change git's behavior at all. It is useful only

Re: [PATCH v2] docs: note that extensions.compatobjectformat is incomplete

[brian m. carlson]

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On 2025-08-25 at 22:46:26, Junio C Hamano wrote:
> Much better.  Let's further do "This option" -> "This extension", as
> all the others described in this document call themselves as such.

Great, I've just sent a v3 that does that.
-- 
brian m. carlson (they/them)
Toronto, Ontario, CA

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Re: [PATCH v2] docs: note that extensions.compatobjectformat is incomplete

[Junio C Hamano]

"brian m. carlson" <sandals@crustytoothpaste.net> writes:

> On 2025-08-25 at 22:46:26, Junio C Hamano wrote:
>> Much better.  Let's further do "This option" -> "This extension", as
>> all the others described in this document call themselves as such.
>
> Great, I've just sent a v3 that does that.

As there are two of them, I'll use my local fixup! instead ;-)