For me git clean -f removed all *.oig files. And keeps the ones that were already there before.
This is what it (almost) looked like after the merge:
$ git status
On branch feature/xyz
Your branch is ahead of 'origin/feature/xyz' by 568 commits.
(use "git push" to publish your local commits)
Untracked files:
(use "git add <file>..." to include in what will be committed)
.idea/codeStyles/
.idea/misc.xml.orig
.idea/codeStyles/ was already there before the merge as an untracked file. .idea/misc.xml.orig (and a lot more) had to be removed.
=> Using git clean -f:
$ git clean -f
Removing .idea/misc.xml.orig
resulted in:
$ git status
On branch feature/xyz
Your branch is ahead of 'origin/feature/xyz' by 568 commits.
(use "git push" to publish your local commits)
Untracked files:
(use "git add <file>..." to include in what will be committed)
.idea/codeStyles/