Overhaul Spack's URL parsing (#2972)

* Remove fake URLs from Spack

* Ignore long lines for URLs that start with ftp:

* Preliminary changes to version regexes

* New redesign of version regexes

* Allow letters in version-only

* Fix detection of versions that end in Final

* Rearrange a few regexes and add examples

* Add tests for common download repositories

* Add test cases for common tarball naming schemes

* Finalize version regexes

* spack url test -> spack url summary

* Clean up comments

* Rearrange suffix checks

* Use query strings for name detection

* Remove no longer necessary url_for_version functions

* Strip off extraneous information after package name

* Add one more test

* Dot in square brackets does not need to be escaped

* Move renaming outside of parse_name_offset

* Fix versions for a couple more packages

* Fix flake8 and doc tests

* Correctly parse Python, Lua, and Bio++ package names

* Use effective URLs for mfem

* Add checksummed version to mitos

* Remove url_for_version from STAR-CCM+ package

* Revert changes to version numbers with underscores and dashes

* Fix name detection for tbb

* Correctly parse Ruby gems

* Reverted mfem back to shortened URLs.

* Updated instructions for better security

* Remove preferred=True from newest version

* Add tests for new `spack url list` flags

* Add tests for strip_name_suffixes

* Add unit tests for version separators

* Fix bugs related to parseable name but in parseable version

* Remove dead code, update docstring

* Ignore 'binary' at end of version string

* Remove platform from version

* Flip libedit version numbers

* Re-support weird NCO alpha/beta versions

* Rebase and remove one new fake URL

* Add / to beginning of regex to avoid picking up similarly named packages

* Ignore weird tar versions

* Fix bug in url parse --spider when no versions found

* Less strict version matching for spack versions

* Don't rename Python packages

* Be a little more selective, version must begin with a digit

* Re-add fake URLs

* Fix up several other packages

* Ignore more file endings

* Add parsing support for Miniconda

* Update tab completion

* XFAILS are now PASSES for 2 web tests

var/spack/repos/builtin/packages/root/package.py

@@ -30,7 +30,7 @@
 class Root(Package):
     """ROOT is a data analysis framework."""
     homepage = "https://root.cern.ch"
-    url      = "https://root.cern.ch/download/root_v6.07.02.source.tar.gz"
+    url      = "https://root.cern.ch/download/root_v6.06.06.source.tar.gz"
 
     version('6.06.06', '4308449892210c8d36e36924261fea26')
     version('6.06.04', '55a2f98dd4cea79c9c4e32407c2d6d17')
@@ -83,7 +83,3 @@ def setup_dependent_environment(self, spack_env, run_env, dependent_spec):
         spack_env.set('ROOTSYS', self.prefix)
         spack_env.set('ROOT_VERSION', 'v6')
         spack_env.prepend_path('PYTHONPATH', self.prefix.lib)
-
-    def url_for_version(self, version):
-        """Handle ROOT's unusual version string."""
-        return "https://root.cern.ch/download/root_v%s.source.tar.gz" % version