- Previously, Spack didn't check the arguments you put in version()
directives.
- So, you could do something like this, where there are arguments for a
URL fetcher AND for a git fetcher:
version('1.0', md5='abc123', git='https://foo.bar', commit='feda2343')
- Now, we check the arguments before constructing a fetcher, to ensure
that each package has *only* arguments for a single type of fetcher.
- Also added `test_package_version_consistency()` to the `package_sanity`
test, so that all builtin packages are required to have valid
`version()` directives.