tests/test-default-push.t

patchbomb: make it easy for the user to decline sending an intro message.

- prompt(): respect interactive mode; clarify logic a bit
- rename introneeded() to introwanted() and give it only one caller
- add 'numbered' arg to makepatch() so it does not need to call
  introwanted()
- factor makeintro() out of getpatchmsgs(), so it's easier to skip the
  intro message based on the user's behaviour

Unexpected but perfectly reasonable side effect: in non-interactive
mode, we don't show unanswerable "Cc" or "From" prompts anymore, so
remove those from the test expectations.

  $ hg init a

  $ echo a > a/a
  $ hg --cwd a ci -Ama
  adding a

  $ hg clone a c
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg clone a b
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ echo b >> b/a
  $ hg --cwd b ci -mb

Push should push to 'default' when 'default-push' not set:

  $ hg --cwd b push
  pushing to $TESTTMP/a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files

Push should push to 'default-push' when set:

  $ echo 'default-push = ../c' >> b/.hg/hgrc
  $ hg --cwd b push
  pushing to $TESTTMP/c
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files