Custom git diff to ignore some conflicts

Question

Hello,

I'm starting tests to move from cvs to git, and I have a problem on all my tests.

We maintain a custom copy of FreeBSD sources, so in cvs we do the following when a new FreeBSD version is released:

1. Import new freebsd src as a vendor branch
2. Merge changes on HEAD

I tried to do the same with git, and it worked, but almost all FreeBSD files have a custom Id like this:

$FreeBSD: release/7.0.0/COPYRIGHT 175036 2008-01-01 09:36:30Z imp $

These lines always change, and because of the place they are stored in the svn repository (release/7.0.0, 7.1.0, 7.2.0), git generates a lot of conflicts that needed to be fixed manually.

I would like to know if there is a way to configure git to just ignore diffs on these lines and use the new one without asking.

I can do it with diff command ignoring those lines, like this:

diff -q -I'[$]FreeBSD:.*$'

Thank you in advance.

Answer 1

I am not sure you can avoid conflict during merges because of those changes.

What you can do, though, is a little script able to list all files to be merges, do your diff -q -I'[$]FreeBSD:.*$' on each of them, and for those with no differences, do a

git checkout --theirs theFreeBSDFile

then a resume of the merge will be able to comple the conflicting merge.

The 'git checkout --theirs' check out stage #3 (theirs) for unmerged paths.

Actually, a git mergetool would be perfect for the job: just before a merge involving FreeBSD files, set your mergetool utility to that script, as described in the question Is it possible for git-merge to ignore line-ending differences?.
If you setup the mergetool config to trust the exit code of that script, any file which does not display any differences except FreeBSD custom lines would be 'git checkout --theirs' and reportedly "merged", the other would not be merged by the same script.
At the end, if a resume still show conflicting file, reset your merge tool to your favorite difftool, and resolve the remaining conflicting files.