Re: git format-patch on empty commit

From: Junio C Hamano <gitster@pobox.com>
Date: Jan 11, 2016, 21:04 UTC
Message-ID: <xmqqegdnx1xx.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <20160111205347.GA14535@sigill.intra.peff.net>

Jeff King <peff@peff.net> writes:

Show 22 quoted lines

> On Mon, Jan 11, 2016 at 02:19:52PM +0000, pedro rijo wrote:
>
>> Couldn't find any explanation on git docs on this issue:
>> 
>> If I create a dummy commit, with some dummy diff, I get a normal patch
>> when I run
>> 
>> $ git format-patch -1 -o outgoing/ -p -k
>> 
>> but if the last commit is an empty commit, generated by
>> 
>> $ git commit --allow-empty "Some commit message"
>> 
>> then the output of the format patch will be an empty patch. If the
>> first case produces something like this:
>
> I'm not sure if this is a bug or not.
>
> In the beginning, git's revision-traversal machinery generally does not
> show commits which have no diff. Over the years, commands like "git log"
> learned to set the "always_show_header" option to show even empty
> commits. But format-patch never did.

The patch based workflow support is geared towards helping the recipient of the patches a lot more than the contributors, and to prevent mistakes while applying the patches, "am" would stop when it sees such an empty e-mail as you saw (in the later part of message I am not quoting). After all, a "format-patch" output that does not have any patch would be indistinguishable from discussion e-mail messages and the recipient would not want to end up with no-op commits that record such messages.

So I think skipping no-op commit from the output was done pretty much deliberately and it is definitely not a bug. I however do not think it is incorrect to say that it is a lack of feature that nobody so far found necessary or beneficial.

I would not refuse to consider adding a new option to "format-patch" to emit such a no-op message, and add a "having no patch is OK, just record a no-op commit" option to "am", though. But I do not see a clear benefit from such change--it sounds more like a set of "because we could" not "because we need to" changes to me.

Thanks.