Re: [PATCH 0/6] Importing and exporting stashes to refs

From: brian m. carlson <sandals@crustytoothpaste.net>
Date: Mar 10, 2022, 21:04 UTC
Message-ID: <Yipn+UiRw/GL6u2Y@camp.crustytoothpaste.net>
In-Reply-To: <xmqq35jpei18.fsf@gitster.g>

On 2022-03-10 at 19:14:59, Junio C Hamano wrote:

Show 24 quoted lines

> "brian m. carlson" <sandals@crustytoothpaste.net> writes:
> 
> > ...  The commits used in a stash export are nearly
> > identical to those used in the stashes, with one notable change: the
> > first parent of a stash is a pointer to the previous stash, or an empty
> > commit if there is no previous stash.  All of the other parents used in
> > the stash commit are present following it in their normal order.
> > ...
> > We intentionally attempt to exactly round-trip commits between stashes,
> > although we don't do so for the exported data due to the base commit not
> > having identical timestamps.  Preserving the commits exactly lets us
> > more efficiently test our code and it also permits users to more easily
> > determine if they have the same data.
> 
> Hmph, out of reflog entries stash@{0}, stash@{1}, stash@{3}, if we
> create a chain of commits A, B, C such that
> 
> 	A^2 = B, A^1 = stash@{0}
> 	B^2 = C, B^1 = stash@{1}
> 	         C^1 = stash@{2}
> 
> then the original stash entry commits can be recreated identically,
> and after you export the stash as "A", you can "import" from it
> without creating any new commit to represent the stash entries, no?

True, that's an alternative approach. Mine has the nice ability that you can see the items in the stash with log --first-parent, which I found to be useful in my testing. We could of course change yours to have that property as well by reversing the order, but then the last item in the chain would have a base commit or a different pattern.

Yours does have the nice ability that we can see the actual original stash commits as well.

> When we create A, if we use a predictable commit log message and
> the same author/committer ident as A^1 (i.e. stash@{0}), and do it
> the same for B and C, then no matter who exports the stash and at
> which time, we'd get an identical result, I would presume.

True.

I do want to preserve my nice --first-parent property. What I propose to do is this: I'll take your approach and reverse the parents to preserve the --first-parent chain and synthesize a predictable root commit based on the fake ID information we use for stashes when nobody's provided any.

-- 
brian m. carlson (he/him or they/them)
Toronto, Ontario, CA