This case is _really_ slow even although it's something we encourage
people to run often and build systems often do. The `brew --prefix`
case is really fast because it's just in Bash so: let's pull the
`brew --prefix <formula>` case into Bash too.
This doesn't handle any edge-cases like `--installed` and the formula
detection is pretty simple.
Also, to make this behaviour consistent, never output `Cellar` paths
from the (Ruby) `brew --prefix`; we never want people relying on the
Cellar paths anyway, only output them if the formula wasn't installed
(where, arguably, using a Cellar path is even worse) and the speedup is
worth this deviation in behaviour.
The shared-mime-info formula and the mactex cask currently install into
locations that are picked up by `brew --prefix --unbrewed`. This leads
to a very large number of files being found.
Before:
```
❯ brew --prefix --unbrewed | wc -l
206735
```
After
```
❯ brew --prefix --unbrewed | wc -l
3
```
Return `opt_prefix` if it exists and `prefix` is not called from within
the same formula's `install` or `post_install` methods. Otherwise, fall
back to the existing functionality.
This avoids the need to use `opt_prefix` etc. everywhere and generally
means we don't expose an implementation detail (i.e. the full Cellar
path) to dependents that have a habit of hard-coding it.
Rationale: everyone thinks it points to the currently installed prefix, not the prefix of the formula that is newest and maybe not installed.
The previous behavior was unintentional and evidence proves it is not intuitive either.
I anticipate no regressions. And hope I am right!
The code was sucking. To the extent that maintenance was hard. It's a lot
easier to work with code that is sensibly split at sensible boundaries. So
now it is more like that.
But the refactor is minimal. Because we don't want you to have more merge
hell than absolutely necessary.
If you merge you will need to pay attention to brew.h.rb (as it is deleted)
and bin/brew (as command logic is gone). It will be painful, but you will just
have to help git out by moving any changes around manually.
Note compatibility.rb. It ensures that any function renames or removals don't
break anything. We're pretty serious about backwards compatibility. And that's
because we encourage you to hack around with the innards. And we couldn't do
that if we would then just make stuff disappear behind your back.
