tests/test-fix-clang-format.t

discovery: fix docstring of `outgoing` class

Also, introduce a more correct name `ancestorsof` for what was named
`missingheads` before. For now, we just forward `ancestorsof` to `missingheads`
until all users are changed.

There were some mistakes in the old docstring / name:

* `missingheads` (new name: `ancestorsof`) contains the revs whose ancestors
  are included in the outgoing operation. It may contain non-head revs and revs
  which are already on the remote, so the name "missingheads" is wrong in two
  ways.
* `missing` contains only ancestors of `missingheads`, so not *all nodes*
  present in local but not in remote.
* `common` might not contain all common revs, e.g. not some that are not an
  ancestor of `missingheads`.

It seems like the misleading name have fostered an actual bug (issue6372),
where `outgoing.missingheads` was used assuming that it contains the heads of
the missing changesets.

#require clang-format

Test that a simple "hg fix" configuration for clang-format works.

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > fix =
  > [experimental]
  > evolution.createmarkers=True
  > evolution.allowunstable=True
  > [fix]
  > clang-format:command=clang-format --style=Google --assume-filename={rootpath}
  > clang-format:linerange=--lines={first}:{last}
  > clang-format:pattern=set:**.cpp or **.hpp
  > EOF

  $ hg init repo
  $ cd repo

  $ printf "void foo(){int x=2;}\n" > foo.cpp
  $ printf "void\nfoo();\n" > foo.hpp
  $ hg commit -Am "foo commit"
  adding foo.cpp
  adding foo.hpp
  $ hg cat -r tip *
  void foo(){int x=2;}
  void
  foo();
  $ hg fix -r tip
  $ hg cat -r tip *
  void foo() { int x = 2; }
  void foo();

  $ cd ..