John Keeping [off-list ref] writes:
You could use a temporary index and do something like:
rm -f TMP_INDEX
GIT_INDEX_FILE=TMP_INDEX
export GIT_INDEX_FILE
git read-tree -m $base $ours $theirs &&
git merge-index git-merge-one-file -a
then inspect that with "git diff-index --cached $ours".
Good.
Note that this will fail if there are conflicts and I don't know what
git-merge-tree will do in that case.
I _think_ Charlies's use case is to detect trivial merges to tell
the requestee that a merge request can be done on site, so failing
is fine when there are conflicts. merge-tree should report
conflicts as well.