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

From: Junio C Hamano <[email-masked]>
Date: Thu, 20 May 2021 13:58:10 +0900

Bagas Sanjaya <[email-masked]> writes:

> 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).