On Mon, Feb 7, 2022 at 10:48 AM Han-Wen Nienhuys [off-list ref] wrote:

On Fri, Feb 4, 2022 at 12:06 AM Junio C Hamano [off-list ref] wrote:

quoted

Han-Wen Nienhuys [off-list ref] writes:

quoted

Technically, the only obstacle I see is that we'd need to treat an
existence entry especially for the purpose of compaction/gc: we can
discard older entries, but we shouldn't discard the existence bit, no
matter how old it is.

I was hoping that we already have a type of block that can be used
to record an attribute on the ref (other than its value) and it
would be just the matter of stealing one unused bit from such a
record per ref to say "when answering 'does this ref have reflog?'
say yes even when there is no log record for that refname".  Or the
table format is extensible enough that we can add such a block
without breaking existing clients.

That place doesn't exist, unfortunately, but even if it did, having a
special reflog entry indicating existence is a better solution all
around, I think. A separate per-ref bit allows for data
inconsistencies: what if the bit says "there is no reflog", but we
actually do have reflog entries in the 'g' section?

It also has less chances of creating complicated control flows
(especially in JGit which wasn't designed for this bit from the
start): the tables have to be written in lexicographic order, so you
only can write this bit after you know if reflog entries were written
for a certain ref.

Correction. I wish the table blocks were written in lexicographic
order, but they are written in order 'g', ['i',] 'o', ['i'], 'g',
['i']. Since the 'g' block is last within a table, we could add a new
section at the end.  My point that this is considerable work to think
through how to make this work with JGit still stands, though.

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