Re: [PATCH] docs/format-patch: mention handling of merges

[Jeff King <peff@peff.net>]

On Mon, Feb 22, 2021 at 03:31:53PM -0800, Junio C Hamano wrote:

> Jeff King <peff@peff.net> writes:
> 
> > Subject: [PATCH] docs/format-patch: mention handling of merges
> >
> > Format-patch doesn't have a way to format merges in a way that can be
> > applied by git-am (or any other tool), and so it just omits them.
> > However, this may be a surprising implication for users who are not well
> > versed in how the tool works. Let's add a note to the documentation
> > making this more clear.
> > ...
> > +CAVEATS
> > +-------
> > +
> > +Note that `format-patch` cannot represent commits with more than one
> > +parent (i.e., merges) and will silently omit them entirely from its
> > +output, even if they are part of the requested range.
> 
> 
> I think "cannot represent" is a little bit misleading, unless we
> expect the readers already know what we are trying to say (in which
> case there is no point in documenting this).  Perhaps something like
> this might clarify a bit, though.
> 
>     Note that `format-patch` omits merge commits from the output,
>     because it is impossible to turn a merge commit into a simple
>     "patch" in such a way that allows receiving end to reproduce the
>     same merge commit.

That seems worse to me, because "it is impossible" implies that this
can never be changed. But I don't think that's true. We might one day
output something useful for merges.

I think one could argue that any merge information (including conflict
resolution) works against the root notion of format-patch, which is a
set of changes that can be applied on a range of basesa. But even that I
would be hesitant to commit to (since --base exists now). And certainly
it's more subtlety than I'd want to get in to for this note. :)

I almost softened it to "cannot yet represent". Does that read better to
your (or worse)? Likewise, I considered adding a note at the end along
the lines of "this may change in the future", though I suspect we'd only
do so in combination with a command-line option.

-Peff