Re: [PATCH] revisions(7): clarify that most commands take a single revision range

From: Junio C Hamano <gitster@pobox.com>
Date: May 20, 2021, 04:58 UTC
Message-ID: <xmqqh7iyuhlp.fsf@gitster.g>
In-Reply-To: <ab2d8b16-42db-9675-083a-efa7cfca6e4c@gmail.com>

Bagas Sanjaya <bagasdotme@gmail.com> writes:

Show 16 quoted lines

> On 18/05/21 18.17, Junio C Hamano wrote:
>> ...
>> +In other words, writing two "two-dot range notation" next to each
>> +other, e.g.
>> +
>> +    $ git log A..B C..D
>> +
>> +does *not* specify two revision ranges for most commands.  Instead
>> +it will name a single connected set of commits, i.e. those that are
>> +reachable from either B or D but are reachable from neither A or C.
>> +In a linear history like this:
>> +
>> +    ---A---B---o---o---C---D
>> +
>
> So "git log A..B C..D" is same as "A..D", right?

A..B C..D is equivalent to ^A ^C B D, and in order to be part of the set it represents, a commit must not be reachable from A, must not be reachable from C, and must be reachable from B or D.

In the picture, A, B and two o's are all reachable from C, therefore are not part of the set A..B C..D represents. Neither is C, as it is reachable from C. That leaves only D in the resulting range.

A..D is a set of connected five commits, B o o C D in the above picture.

So, no.

The confusion we often see goes more like "The set A..B contains B (and nothing else), and C..D contains D (and nothing else), hence 'git log A..B C..D' would show B and D". But that is not what happens because "git log" (like most other commands) takes just a "range" that is "A..B C..D", which is a set of connected commits each of whose member is reachable from one of the "positive" endpoints (like B and D) and is not reachable from any of the "negative" endpoints (like A and C).