On Wed, May 20, 2020 at 6:06 PM Han-Wen Nienhuys <hanwen@xxxxxxxxxx> wrote:
> > > +The `message_length` may be 0, in which case there was no message
> > > +supplied for the update.
> > > +
> > > +Contrary to traditional reflog (which is a file), renames are encoded as
> > > +a combination of ref deletion and ref creation.
> >
> > Yay? How does the deletion record look like? The new object name
> > being 0*hashlength? I didn't see it defined in the description (and
> > I am guessing that log_type of 0x0 is *NOT* used for that purpose).
>
> quoting the spec:
>
> "Log record entries use `log_type` to indicate what follows:
>
> * `0x0`: deletion; no log data."
>
> > So, NEEDSWORK: describe how "creation of a ref" and "deletion of a ref"
> > appears in a log as a log record entry.
>
> the creation would be the appearance of a reflog record for the ref.
> You'd have to search back in time to decide if a reflog record it was
> an update to an existing record or a creation.
Correction. This is one of the things that confused me earlier: reflog
entries for creating and deleting branches look like this
000000000000 -> xxxxx (create)
xxxxxx.. xx -> 00000 .. (delete)
respectively. When the rename happens, we can signal that the deletion
and addition are linked, because they occur at the same update_index.
The deletion records for logs (type=0x0) remove a reflog entry at a
specific (earlier used) update_index. So you could have the following
situation:
0x0001.ref : reflog "refs/heads/master" @ update_index=0x0001,
new=xxx, old=yyy ...
and then a subsequent table could specify
0x0020.ref : reflog "refs/heads/master" @ update_index=0x0001 (type=0x0)
which would hide the earlier reflog entry.
Jonathan Nieder said that this is used for git-stash, but I have never
understood why this is necessary, and would love to clarify this
better.
I'll clarify the explanation to reflect this.
--
Han-Wen Nienhuys - Google Munich
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