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
Create an empty repo:
$ hg init a
$ cd a
Try some commands:
$ hg log
$ hg grep wah
[1]
$ hg manifest
$ hg verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
0 files, 0 changesets, 0 total revisions
Check the basic files created:
$ ls .hg
00changelog.i
requires
store
Should be empty:
$ ls .hg/store
Poke at a clone:
$ cd ..
$ hg clone a b
updating to branch default
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd b
$ hg verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
0 files, 0 changesets, 0 total revisions
$ ls .hg
00changelog.i
hgrc
requires
store
Should be empty:
$ ls .hg/store
$ cd ..