Problem with git merge/rebase with conflicts

I'm writing about merging and rebasing with conflicts, and there's something weird with it -- after this setup:

  mkdir /tmp/r1; cd /tmp/r1; git init
  echo foo > file; git add file; git commit -m first
  cd /tmp; git clone r1 r2
  cd /tmp/r1; echo abc > file; git commit -m abc file
  cd /tmp/r2; echo xyz > file; git commit -m xyz file
  git fetch

1. I get this:

     $ git merge origin
     ...CONFLICT...
     $ git status -s
     UU file
     $ echo xyz > file
     $ git add file
     $ git status -s

   and there's nothing -- it's all clean after that `add', without
   committing and without anything said.  If this is intentional, it
   would be nice if there was some message from `git add'...  And it
   would also be nice if I'd seen it mentioned anywhere, but
   practically everything I've read said the same: `git add' and then
   `git commit', no mention of that second step being optional.

2. I have some other sample repository that exhibits the behavior with
   the "resolution" going the other way, but here -- starting from the
   same setup:

     $ git merge origin
     ...CONFLICT...
     $ echo abc > file
     $ git add file
     $ git status -s
     M  file
     $ git commit
     ...get an editor without the conflict resolution template thing...
     $ git log --graph --all --oneline
     * 2d3744b Huh?
     * 98c46da xyz
     | * 4744b19 abc
     |/  
     * c8915c2 first

   This looks like I never did any merge.

     $ git merge origin
     Merge made by recursive.
     $ git log --graph --all --oneline
     *   94e69e9 Merge remote branch 'origin'
     |\  
     | * 4744b19 abc
     * | 2d3744b Huh?
     * | 98c46da xyz
     |/  
     * c8915c2 first

   And this looks even more wrong...

3. Again, starting from the same setup:

     $ git rebase origin
     ...CONFLICT...
     $ git status -s
     UU file
     $ echo abc > file
     $ git add file
     $ git status -s
                       <- nothing
     $ git rebase --continue
     Applying: xyz
     No changes - did you forget to use 'git add'?

   which is probably related to the above.  I could use --skip, but
   now that I edited it manually I can't remember that --skip does
   what I already did.