From: John Keeping <john@keeping.me.uk>
Date: Mon, 05 Oct 2015 20:34:32 GMT
Subject: Re: How can I ignore insignificant change during merge ?
Message-ID: <20151005203432.GR17201@serenity.lan>
In-Reply-To: <CA+aSyzqxjoUbGbPvLMNcrYyE3ZAqwGYiXtSrUgg8O29MZLJWrA@mail.gmail.com>

On Mon, Oct 05, 2015 at 10:13:00PM +0200, Jens Brejner wrote:
> I need to merge a branch, +100k changes. The vast majority of changes
> are insignificant, because they only represent a screen position in
> the editor, so these changes should never have been in git - but but
> MadCap Flare already put them there.
> 
> The files in question are xml, and the difference can be exemplifed like this:
> 
> Original (when branches were created):
> html xmlns:MadCap="http://www.madcapsoftware.com/Schemas/MadCap.xsd"
> MadCap:lastBlockDepth="5" MadCap:lastHeight="32"
> MadCap:lastWidth="400"
> Branch1:
> html xmlns:MadCap="http://www.madcapsoftware.com/Schemas/MadCap.xsd"
> MadCap:lastBlockDepth="5" MadCap:lastHeight="24"
> MadCap:lastWidth="500"
> Branch2:
> html xmlns:MadCap="http://www.madcapsoftware.com/Schemas/MadCap.xsd"
> MadCap:lastBlockDepth="5" MadCap:lastHeight="41"
> MadCap:lastWidth="300"
> 
> How can git help me so files where the only difference matches
> something like this regex:
> /html xmlns:.* MadCap:lastHeight="\d+" MadCap:lastWidth="\d+"/
> 
> for the files that qualify, I want git to ignore the change, and
> therefore the merge-conflict, and then just accept "my" file for the
> merged changeset.
> 
> Any suggestions on how to I can have git help me with that ?

Have you looked into defining a custom merge driver for these files?
It's documented in the "Performing a three-way merge" section of
gitattributes(5) - that is, "git help attributes".

It should be relatively easy to ignore these changes, but you'll have to
deal with merging the rest of the files as well; Python's difflib module
may be useful.