Expand requirements recursively while applying the same optional? and
recommended? filters that dependencies are run through. Options
generated by requirements are now checked against the correct list of
requirements, eliminating the temporary "best guess" logic in the
installer.
When a formula's dependency tree contains more than one X11 dependency,
they are de-duplicated by comparing the min_version attribute. However,
this can result in broken dependency trees if one of the X11Dependency
objects was actually specified as e.g. `:libpng`.
In practice, this only matters when one or more of the dependencies has
additional metadata that makes it distinct from the rest, i.e. an
:optional or :recommended tag.
To combat this, make these special, "partial" X11 dependencies instances
of different classes so that they are not de-duped.
It will still be necessary, at the time when requirements are expanded
by the installer, to de-duplicate any remaining X11 dependencies after
applying the optional/recommended filters in order to avoid duplicated
modifications to the environment (as ENV.x11 is not idempotent).
c.f. Homebrew/homebrew#17369.
Also, move the line containing `info`, `home` and `options` to the top of the
list as users should be running these before installation.
Ref. Homebrew/homebrew#13224.
We skip build-time deps when installing from bottles. However, the
current logic only considers the root, rather than the actual dependent
formula. Given
A (bottled)
|__B (not bottled)
|__C (build-time)
C will be pruned from the effective dependency tree of A. This is wrong,
because C is required in order to build B.
Fix this by examining the current dependent rather than the root.
FixesHomebrew/homebrew#17356.
Since 'gcc' is a symlink to 'llvm-gcc' on Xcode 4.3+, --use-gcc and
--use-llvm were doing exactly the same thing. Combined with the
previous commit, this allows users with either a leftover
/usr/bin/gcc-4.2 or a homebrewed apple-gcc42 to build with gcc.
This doesn't however fix Xcode-only systems with apple-gcc42.
FixesHomebrew/homebrew#17243.
