These formulae are detected as missing but exist in an unreadable form.

Fixes #2485

GitHub provides a description and homepage field so let `brew create`
use them where possible. Also, detect GitHub repositories based on
`releases` as well as `archive`s.

Add `--only` and `--except` methods which can be used to selectively
enable or disable audit groups.

This is useful for seeing when formulae are deleted if they are going to
leave behind any formulae that depend on them.

As a result, if there are any formulae returned return a non-zero/failed
exit status.

As requested in #11462 by @neutric as this produces confusing,
incorrect output.

Make `brew audit` complain about language module requirements because
they provide a crappy user experience compared to vendoring and we’re
not really fixing bugs in them any more.

Also check for `ENV.universal_binary` and `build.universal?`. The prior
is still required for `wine` and the latter should never be required any
longer.

This check for a nil `tap` is necessary because Tap.from_path(path)
will simply return a nil value in the event the tap path is invalid

Our CI images are already updated with it.

Was missing a formula object being passed.

These were those migrated from other taps but if they are installed
already: they aren't new to that user.

Signed-off-by: Bob W. Hogg <rwhogg@linux.com>

For example if this is for a really old keg, keg where a user has
manually removed stuff or used `brew diy`.

ln_sf does the right thing when `dest` is a symlink pointing to a file:
the symlink gets overwritten with a link pointing to the new src. But
when dest points to a directory, we create a new symlink inside the
folder dest points to, which doesn't help us at all.

When we're assessing whether a bottle is relocatable, we shouldn't have
to descend into symlink paths we encounter. This is supposed to be the
default behavior but it doesn't appear to be (perhaps because we pass a
symlink to the keg on the command line?).

All of the switches that control this behavior differ between BSD and
GNU grep, so sniff the grep flavor first.

Commit 4cae6a72 introduced the message,
but it printed the wrong path, e.g. for `brew link sqlite`:

```
If you need to have this software first in your PATH instead consider running:
  echo 'export PATH="/usr/local/opt/sqlite:$PATH"' >> ~/.zshrc/bin
```

where `/bin` is appended at the end, but should be inserted before
`:$PATH`: `echo 'export PATH="/usr/local/opt/sqlite/bin:$PATH"' >> ~/.zshrc`.
This patch fixes that and updates a test to verify it.

maintain existing compatibility with gnupg 2.0.x

Fixes #2427.