Git: get ours/theirs file content during merge

Hidden in the docs :

git show :1:file/path   # base
git show :2:file/path   # ours
git show :3:file/path   # theirs

---

When a merge conflict is triggered because of a merge action, HEAD still points to the original commit, and MERGE_HEAD to the commit trying to be merged in, so :

git show HEAD:file/path        # ours
git show MERGE_HEAD:file/path  # theirs

will also work, and perhaps be more explicit to the user.