Simplify code by not passing local data to methods
Add an experimental "--mergeup" flag to use a less volatile merge strategy in "arc land"

Summary:
See chatlog from https://secure.phabricator.com/chatlog/channel/%23phabricator/?at=37257

Basically, the install's developers sometimes use "git merge master" instead of "git rebase master" to pull changes from master into their branch. When we run "git rebase master" at the end, this creates a lot of conflicts.

Instead, optionally run "git merge master". This should be equivalent in our case (where we always rebase) and much better in their case (where they sometimes merge).

We're both going to use it for a bit and see if it creates problems. If it improves the "sometimes-merge" workflow without affecting the "always rebase" workflow, we can make it a default. If it improves theirs but damages ours, we can keep it a flag/option. If it's just terrible, we can figure out something else.

Test Plan:
Ran `arc land --mergeup --trace <feature> --keep-branch --hold`, see P624 for output. Observed merge update strategy and general success.

Also verified the conflict:

  $ arc land --mergeup --merge
  Usage Exception: Arguments '--mergeup' and '--merge' are mutually exclusive: The --merge strategy does not update the feature branch.

Reviewers: btrahan, vrana, DurhamGoode

Reviewed By: btrahan

CC: aran, keir

Differential Revision: https://secure.phabricator.com/D4080
add arc land hg support for landing with nested branches

Summary:
This changes arc land's hg support to allow you to land a branch or bookmark that has nested branches/bookmarks.  Example:

      // Initial state:
      // -a--------b  master
      //   \
      //    w--x  mybranch
      //        \--y  subbranch1
      //         \--z  subbranch2
      //
      // arc land --branch mybranch --onto master :
      // -a--b--wx  master
      //          \--y  subbranch1
      //           \--z  subbranch2

Test Plan:
Created several repos like in the summary and ran 'arc land' and 'arc land --keep-branch'. Did this with both bookmarks and named branches. Scenarios tested:

- mybranch having no child commits
- mybranch having a child branch with several commits
- mybranch having two child branches
- mybranch having a child branch which has two more child branches

No code was added outside of a "if ($this->isHg)" so I didn't run git arc land.

Reviewers: epriestley, dschleimer, bos, sid0

Reviewed By: dschleimer

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4089
Update PEP8

Test Plan:
Linted this Python file:

  def get_mapper_sets(
          compression=4.0,  # Currently works for most tables
          **kwargs):
      pass

Didn't see:

> E225 missing whitespace around operator

Reviewers: andrewjcg, epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4172
Suggest upgrading Phabricator for unknown Conduit methods or parameters

Summary:
This allows using new methods without the need for bumping version number.

The usage is not neccessary because we already bumped the version number for this but I wanted to have a callsite.

Test Plan:
Made a typo in method name, then:

  $ arc lint --only-new 1

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4193
Merge branch 'master' of http://github.com/facebook/arcanist