# [BUG?] "format-patch --range-diff=$commit HEAD^ HEAD" fails

2 messages from 2024-04-19 to 2024-04-20. Participants: Junio C Hamano.
Thread: https://gitlist.dev/t/61339

## Junio C Hamano, 2024-04-19 17:17

Subject: [BUG?] "format-patch --range-diff=$commit HEAD^ HEAD" fails
Message-ID: <xmqqbk65jmqp.fsf@gitster.g>
URL: https://gitlist.dev/e/xmqqbk65jmqp.fsf%40gitster.g

```
Immediately after "git commit --amend" of a single commit,
this fails:

    $ git format-patch --range-diff=@{1} -v2 HEAD^ HEAD
    fatal: --range-diff requires --cover-letter or single patch

The intent is very clear.  I know it is a single-patch topic, and I
want to show what I changed with "commit --amend" as a reference to
the previous version.  These, on the other hand, that specify the
range of commits to be emitted correctly recognises that we are
talking about a single patch and does not fail.

    $ git format-patch --range-diff=@{1} -v2 HEAD^
    $ git format-patch --range-diff=@{1} -v2 -1

It seems to me that the traditional "format-patch <since> <until>"
notation, which is understood by everywhere else in format-patch, is
not correctly understood by the code for "--range-diff" to make this
complaint, to recognise that the given range has only a single commit.


```

## Junio C Hamano, 2024-04-20 17:30

Subject: Re: [BUG?] "format-patch --range-diff=$commit HEAD^ HEAD" fails
Message-ID: <xmqqcyqk3ps8.fsf@gitster.g>
URL: https://gitlist.dev/e/xmqqcyqk3ps8.fsf%40gitster.g
In-Reply-To: <xmqqbk65jmqp.fsf@gitster.g>

```
Junio C Hamano <gitster@pobox.com> writes:

> Immediately after "git commit --amend" of a single commit,
> this fails:
>
>     $ git format-patch --range-diff=@{1} -v2 HEAD^ HEAD

Please scratch this one.  I simply forgot that we have lost
the

	git format-patch <his> <mine>

syntax long time ago during Git 1.4.0 timeframe [*].  I somehow was
confused since we still have the corresponding

	rebase <since-onto> <mine>

syntax.


[Footnote]
 * I suspect this may not have been a conscious design decision but
   by accident during the rewrite of the command in C that I started
   at 3eefc189 (Tentative built-in format-patch., 2006-04-18) and
   whose final shape was documented by 2052d146 (Update
   documentation for git-format-patch, 2006-05-31).

```