Re: Strange behaviour of git diff branch1 ... branch2

From: Nguyen Thai Ngoc Duy <pclouds@gmail.com>
Date: Oct 27, 2012, 03:51 UTC
Message-ID: <CACsJy8CX4Wbf3Bqez2kcQ7NGYMkqXC8MK+=hrH4iaev+0ZrQ8Q@mail.gmail.com>
In-Reply-To: <20121026212650.GB2612@pug.qqx.org>

On Sat, Oct 27, 2012 at 4:26 AM, Aaron Schrab <aaron@schrab.com> wrote:

Show 12 quoted lines

> I came across this odd question on stackoverflow:
>         http://stackoverflow.com/q/13092854/1507392
>
>
> If git diff is run with "..." as a separate argument between two commit-ish
> arguments causes it to produce strange output.  The differences seem to be
> the same as if "..." was left out, but change lines begin with 4 + or -
> characters rather than just 1.
>
> Can anybody explain what is happening here?  I don't have any reason to want
> to use that form myself, but I'm very curious about why it produces this odd
> output.

I'm curious too. It shows this to me

diff --cc .gitignore index a188a82,a188a82,a188a82,a188a82..d4473d8

--- a/.gitignore
+++ b/.gitignore
@@@@@ -2,9 -2,9 -2,9 -2,9 +2,6 @@@@@
    /GIT-CFLAGS
    /GIT-LDFLAGS
    /GIT-GUI-VARS
----/GIT-PREFIX
----/GIT-SCRIPT-DEFINES
----/GIT-USER-AGENT
    /GIT-VERSION-FILE
    /bin-wrappers/
    /git

Notice the --cc in the first line, which is combined diff. Usually
combined-diff is between two points and one parent. Though somehow git
passes 4 parents down combined-diff.c:show_combined_header, as you can
see in the "index" line. I think we should fix rev parsing code as it
does not make sense to pass 4 identical parents this way.

-- 
Duy