tests/test-releasenotes-merging.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

  $ cat >> $HGRCPATH << EOF
  > [extensions]
  > releasenotes=
  > EOF

  $ hg init simple-repo
  $ cd simple-repo

A fix directive from commit message is added to release notes

  $ touch fix1
  $ hg -q commit -A -l - << EOF
  > commit 1
  > 
  > .. fix::
  > 
  >    Fix from commit message.
  > EOF

  $ cat >> $TESTTMP/single-fix-bullet << EOF
  > Bug Fixes
  > =========
  > 
  > * Fix from release notes.
  > EOF

  $ hg releasenotes -r . $TESTTMP/single-fix-bullet

  $ cat $TESTTMP/single-fix-bullet
  Bug Fixes
  =========
  
  * Fix from release notes.
  
  * Fix from commit message.

Processing again ignores the already added bullet.

  $ hg releasenotes -r . $TESTTMP/single-fix-bullet

  $ cat $TESTTMP/single-fix-bullet
  Bug Fixes
  =========
  
  * Fix from release notes.
  
  * Fix from commit message.

  $ cd ..

Sections are unioned

  $ hg init subsections
  $ cd subsections
  $ touch fix1
  $ hg -q commit -A -l - << EOF
  > Commit 1
  > 
  > .. feature:: Commit Message Feature
  > 
  >    This describes a feature from a commit message.
  > EOF

  $ cat >> $TESTTMP/single-feature-section << EOF
  > New Features
  > ============
  > 
  > Notes Feature
  > -------------
  > 
  > This describes a feature from a release notes file.
  > EOF

  $ hg releasenotes -r . $TESTTMP/single-feature-section

  $ cat $TESTTMP/single-feature-section
  New Features
  ============
  
  Notes Feature
  -------------
  
  This describes a feature from a release notes file.
  
  Commit Message Feature
  ----------------------
  
  This describes a feature from a commit message.

Doing it again won't add another section

  $ hg releasenotes -r . $TESTTMP/single-feature-section
  Commit Message Feature already exists in feature section; ignoring

  $ cat $TESTTMP/single-feature-section
  New Features
  ============
  
  Notes Feature
  -------------
  
  This describes a feature from a release notes file.
  
  Commit Message Feature
  ----------------------
  
  This describes a feature from a commit message.

  $ cd ..

Bullets from rev merge with those from notes file.

  $ hg init bullets
  $ cd bullets
  $ touch fix1
  $ hg -q commit -A -l - << EOF
  > commit 1
  > 
  > .. fix::
  > 
  >    this is fix1.
  > EOF

  $ touch fix2
  $ hg -q commit -A -l - << EOF
  > commit 2
  > 
  > .. fix::
  > 
  >    this is fix2.
  > EOF

  $ hg releasenotes -r 'all()' $TESTTMP/relnotes-bullet-problem
  $ cat $TESTTMP/relnotes-bullet-problem
  Bug Fixes
  =========
  
  * this is fix1.
  
  * this is fix2.
  $ touch fix3
  $ hg -q commit -A -l - << EOF
  > commit 3
  > 
  > .. fix::
  > 
  >    this is fix3.
  > EOF

  $ hg releasenotes -r . $TESTTMP/relnotes-bullet-problem
  $ cat $TESTTMP/relnotes-bullet-problem
  Bug Fixes
  =========
  
  * this is fix1.
  
  * this is fix2.
  
  * this is fix3.