dev-cmd/man: use SOURCE_PATH instead of HOMEBREW_LIBRARY

Don't Repeat Yourself.

More Rubocop tweaks.

- Don't enforce hash rockets on external commands.
- Enabled accidentally disabled ParenthesesAsGroupedExpression.

Update Rubocop style.

install: prune build-only deps of deps

cmd/outdated: group specs of same formula

Compare names not formulae

Add `brew release-notes` developer command.

Another look at the current Rubocop rules and how they fit with our
existing and desired future style. Almost all of these changes were
automatic. Split some rules between formulae/brew where brew doesn't
have millions of cases that need fixed.

Outputs the merged pull requests on Homebrew/brew between two Git refs.

cask/test: DRY up tests and remove redundant helper

brew info: include options to dependencies in display

Refactor `spec_helper`.

hbc/cli/list: don't require Caskroom to be initialized

fix 'cask info' for external repos with numbers

New name and old name must have different names

* Causes a bug in Formula#installed_alias_target_changed? when
  Formula#superseds_an_installed_formula? returns true because
  Formula#old_installed_formulae includes f for some Formula f.

* Causes a bug when foo@2.4 with alias foo has HEAD or devel version and
  we try to `brew upgrade foo --devel|--HEAD` from stable. The upgrade fails
  while since we installing formula to the same prefix it's alredy installed.
  The reason for that is that we use
  `formula_to_install = outdated.map(&:latest_formula)` in cmd/upgrade
  before calling upgrade_formula on foo.

  ```ruby
  def latest_formula
  installed_alias_target_changed? ? current_installed_alias_target : self
  end
  ```

  Formula#installed_alias_target_changed? compares formulae using
  Formula#==, which is wrong for this case, thus Formula#latest_formula doesn't
  return self and returns Formula#current_installed_alias_target with spec
  foo was initially installed instead of devel or HEAD, causing the error.

Suppose you have devel and stable versions of `foo` installed.
Their versions should be grouped together regardless their specs.

Output before the change:
  foo (2.4), foo (3.28-01) < 5.1

Output after the change:
  foo (2.4, 3.28-01) < 5.1

Also use `which` to find `lsar` in PATH.

Unset HOMEBREW_DEVELOPER in cask tests likely to raise deprecation errors

hbc/locations: arg is file only if absolute or .rb file