tests/test-sparse-clear.t

phabricator: use Phabricator's last node information

This makes it more strict when checking whether or not we should update a
Differential Revision. For example,

  a) Alice updates D1 to content 1.
  b) Bob updates D1 to content 2.
  c) Alice tries to update D1 to content 1.

Previously, `c)` will do nothing because `phabsend` detects the patch is not
changed. A more correct behavior is to override Bob's update here, hence the
patch.

This also makes it possible to return a reaonsable "last node" when there is
no tags but only `Differential Revision` commit messages.

Test Plan:
```
for i in A B C; do echo $i > $i; hg ci -m $i -A $i; done

hg phabsend 0::
# D40: created
# D41: created
# D42: created

echo 3 >> C; hg amend; hg phabsend .
# D42: updated

hg tag --local --hidden -r 2 -f D42
# move tag to the previous version

hg phabsend .
# D42: skipped (previously it would be "updated")

rm -rf .hg; hg init
hg phabread --stack D42 | hg import -
hg phabsend .
# D42: updated
hg tag --local --remove D42
hg commit --amend
hg phabsend .
# D42: updated (no new diff uploaded, previously it will upload a new diff)
```

The old diff object is now returned, which could be useful in the next
patch.

Differential Revision: https://phab.mercurial-scm.org/D121

test sparse

  $ hg init myrepo
  $ cd myrepo
  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > sparse=
  > purge=
  > strip=
  > rebase=
  > EOF

  $ echo a > index.html
  $ echo x > data.py
  $ echo z > readme.txt
  $ cat > base.sparse <<EOF
  > [include]
  > *.sparse
  > EOF
  $ hg ci -Aqm 'initial'
  $ cat > webpage.sparse <<EOF
  > %include base.sparse
  > [include]
  > *.html
  > EOF
  $ hg ci -Aqm 'initial'

Clear rules when there are includes

  $ hg debugsparse --include *.py
  $ ls
  data.py
  $ hg debugsparse --clear-rules
  $ ls
  base.sparse
  data.py
  index.html
  readme.txt
  webpage.sparse

Clear rules when there are excludes

  $ hg debugsparse --exclude *.sparse
  $ ls
  data.py
  index.html
  readme.txt
  $ hg debugsparse --clear-rules
  $ ls
  base.sparse
  data.py
  index.html
  readme.txt
  webpage.sparse

Clearing rules should not alter profiles

  $ hg debugsparse --enable-profile webpage.sparse
  $ ls
  base.sparse
  index.html
  webpage.sparse
  $ hg debugsparse --include *.py
  $ ls
  base.sparse
  data.py
  index.html
  webpage.sparse
  $ hg debugsparse --clear-rules
  $ ls
  base.sparse
  index.html
  webpage.sparse