Karthik Nayak [off-list ref] writes:

Patrick Steinhardt [off-list ref] writes:

quoted

On Tue, May 14, 2024 at 02:44:11PM +0200, Karthik Nayak wrote:

quoted

From: Karthik Nayak <redacted>

Add 'symref-update' command to the '--stdin' mode of 'git-update-ref' to
allow updates of symbolic refs. The 'symref-update' command takes in a
<new-target>, which the <ref> will be updated to. If the <ref> doesn't
exist it will be created.

It also optionally takes either an `ref <old-target>` or `oid
<old-oid>`. If the <old-target> is provided, it checks to see if the
<ref> targets the <old-target> before the update. If <old-oid> is provided
it checks <ref> to ensure that it is a regular ref and <old-oid> is the
OID before the update. This by extension also means that this when a
zero <old-oid> is provided, it ensures that the ref didn't exist before.

It's somewhat unfortunate that the syntax diverges from the "update"
command. "update" also has essentially the same issue now, that we
cannot verify that its old value is a symref, right? Can we fix that in
a backwards compatible way?

I think Peff mentioned [1] of a way. So we convert the existing

    update SP <ref> SP <newvalue> [SP <oldvalue>] LF
    update SP <ref> NUL <newvalue> NUL [<oldvalue>] NUL // -z

to

    update SP <ref> SP <newvalue> [SP (<oldvalue> | ref <old_target>)] LF
    update SP <ref> NUL <newvalue> NUL [(<oldvalue> | ref NUL <old_target>)] NUL // -z

this should work, I think. I will play around this and add it in. Please
let me know if you can think of a scenario where this breaks.

Thinking about this more, I'll actually do this in a follow up series. I
want to cleanup the existing tests already to move them to the loop that
I introduced in this series. That would make it easier to test and
ensure that we can port the existing 'update' command to also support
`old_target`.

[snip]