[PATCH 0/3] detecting delete/modechange conflicts

I was surprised to find that:

  # base commit
  echo base >file &&
  git add file &&
  git commit -m base &&

  # one side changes mode
  chmod +x file &&
  git commit -am executable &&

  # the other deletes the file
  git checkout -b other HEAD^ &&
  git rm file &&
  git commit -am removed &&

  git merge master

silently completes the merge, dropping the mode change. We detect delete/modify conflicts, but not delete/modechange conflicts. The trivial index merge does catch it, but both the resolve and recursive strategies resolve it silently in favor of the deletion.

After looking through the history and the list archive, I don't _think_ this was intentional, and we simply missed the case in both places. But maybe somebody else knows something I don't. It seems like we should be punting to the user under the general principle of stupid and safe merges.

  [1/3]: t6031: move triple-rename test to t3030
  [2/3]: t6031: generalize for recursive and resolve strategies
  [3/3]: merge: detect delete/modechange conflict

-Peff