gistfile1.txt

$ git merge -v -X theirs -X renormalize b
Merging:
bd4b397 a
virtual b
found 1 common ancestor:
bf52dc8 init
Auto-merging a.txt
error: addinfo_cache failed for path 'a.txt'
a.txt: unmerged (f1d8608b7f0b6c17e9ebfde7c968f4d8edede18a)
a.txt: unmerged (8b161d9a834fa933934e8d5e1238015ecf46391c)
fatal: git write-tree failed to write a tree

$ git status
On branch a
Your branch is up-to-date with 'origin/a'.

Unmerged paths:
  (use "git reset HEAD <file>..." to unstage)
  (use "git add <file>..." to mark resolution)

        both added:      a.txt