In order to allow kegs built with the same version but differing formula
revisions to coexist, we must encode the revision as part of the keg's
name. This is necessary to actually perform an upgrade, as we cannot
upgrade a keg in-place, and temporarily moving it pending the result of
the upgrade is error-prone and potentially slow.
To accomplish this, we introduce a new Formula#pkg_version method that
concatenates the active_spec version with the formula revision. An
exception is made for a formula that has no revision: the tag is
omitted. This preserves compatibility with existing installations.
Declarations of dependencies, options, and resources in the DSL only
apply to specs that have already been initialized. For example, given
this snippet:
url ...
sha1 ...
depends_on 'foo'
devel do
url ...
sha1 ...
end
The dependency 'foo' will be recorded for the stable spec, but not the
devel spec, since it was not initialized prior to the call to
depends_on.
While it is considered best practice to declare all specs (stable,
devel, head, and bottle) prior to other declarations, there is nothing
that enforces this ordering, so when it happens it can be confusing and
hard to debug.
To prevent this, we can initialize all specs up front. This comes with
a performance penalty for commands that load all formulae into memory,
but that is probably outweighed by what we gain in correctness.
FixesHomebrew/homebrew#23425.
Comparing two objects should not raise an exception, even if they have
different types.
The semantics of #== are now the same as #eql?, so make one an alias.
