tests/test-pull-update.t

run-tests: move diff generation into TestResult

TestResult is the thing that captures all our test results. It's logical
for diff viewing to be handled there and not inside Test.

While writing this patch, it was discovered that Test.fail() was
printing redundant test result output. This has been removed.

Arguments controlling diffs have been removed from Test.__init__.

  $ hg init t
  $ cd t
  $ echo 1 > foo
  $ hg ci -Am m
  adding foo

  $ cd ..
  $ hg clone t tt
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd tt
  $ echo 1.1 > foo
  $ hg ci -Am m

  $ cd ../t
  $ echo 1.2 > foo
  $ hg ci -Am m

Should not update:

  $ hg pull -u ../tt
  pulling from ../tt
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  not updating: not a linear update
  (merge or update --check to force update)

  $ cd ../tt

Should not update:

  $ hg pull -u ../t
  pulling from ../t
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  not updating: not a linear update
  (merge or update --check to force update)

  $ HGMERGE=true hg merge
  merging foo
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -mm

  $ cd ../t

Should work:

  $ hg pull -u ../tt
  pulling from ../tt
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (-1 heads)
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ cd ..