As these may be migrations from another tap where we want to migrate
options across correctly.

In the installation whose prefix is other than /usr/local,
osxfuse library and include path must explicitly be specified during build.
Although brew's pkg-config is configured to prepend appropriates paths,
the prepended paths (/usr/local) supercede the original HOMEBREW_PREFIX.
This behavior will cause the linker to select libraries outside brew's tree.

By adding /usr/local to HOMEBREW_LIBRARY_PATHS, superenv ensures that appears
only after the HOMEBREW_PREFIX, and thus fixes this problem.

HOMEBREW_INCLUDE_PATHS is also configured like keg-only Formulae.

We can filter it just for Clang and let it be used by anything else.

This was implemented before the rest of the file was refactored.

A more widely used style than relying on `if`/`else` returns.

This makes it easier to identify null versions when inspecting them.

installer command accepts -applyChoiceChangesXML option to change
customize options on the GUI installer from the commandline.
(`man installer` for more detailed information)

The introduced option `choice` enables the choice changes to be supplied
via pkg stanza without tricks in preflight code.

When a formula depends on any requirements, they evaluated at most three times:
before locking, before installing dependent, before building formula.
When a non-fatal requirement is specified and thus evaluated three times,
mostly the same warning message is also emitted three times.

This change restricts printing the warning messages only when a bottle is
successfully installed or before building.
Since this timing is after the final dependency computation for each cases,
the warnings will be most useful to check what is not yet satisfied.

This isn't defined for formulae.

Clang has fully implemented OpenMP support as of LLVM 3.7, so if OpenMP
is required by a formula gcc is no longer the only choice of compiler.

Clang should be preferred over gcc because using gcc meant linking
against libstdc++, which is ABI incompatible with libc++. This may be
unnoticeable for some users, but it causes other builds to fail, e.g.
pstoedit when imagemagick was built with OpenMP. pstoedit is required
for the octave formula, so for some users this could be a significant
problem.

Handle `MethodDeprecatedError` because we want people to be able to
uninstall regardless of the content of their formula.

This is also not allowed.

As seen in https://github.com/Homebrew/homebrew-core/pull/6996.

Removes OkJson from vendor/, as Ruby has included its own JSON
parser in corelib since 1.9.x and Homebrew is now guaranteed to be
running on 2.x+.

Fix regression caused by #1364.

For user-supplied PR message.

These are formulae-wide so doesn't make sense to iterate through these
for specs and get weird results.

As seem in https://github.com/Homebrew/homebrew-core/pull/6952.

This reverts commit 50c964df.

This was causing the flaky tests that #1508 started skipping.

This is the second time that `Formula.installed`'s cache has bitten
me with intermittent test failures, and I'd like it to be the last,
so I've made it so the cache is cleared automatically when a tab is
created. This _should_ mean that the cache is cleared any time it
needs to be, with the exception of when a Keg is created artificially
with no tab. I don't think there's anything I can do to automatically
handle that use-case, though.