Refactor spec/version matching.

Instead of choosing the comparison on each `.match()` call, the
expression is converted to a combination of `Range()` expressions
(simple comparison to a semver-compliant `Version`).

`Range()` objects can be combined with `And` and `Or` through the
`AnyOf` and `AllOf` clauses (sticking to Python's naming scheme).

Some specific flags have been provided to those range, allowing users to
subtly alter the matching behaviour - thus accomodating different
versioning schemes:
- `<0.1.2` won't match `0.1.2-rc1`, unless the prerelease_policy flag is
  set to either `always` or `same-patch`
- `<0.1.2` will match `0.1.1-rc1`, unless the `prerelease_policy` flag
  is set to `same-patch`
- `==0.1.2` will always match `0.1.2+build44`, unless the `build_policy`
  is set to `strict`.

The `Spec` item has been updated, alongside `SpecItem`.
Those objects keep the original expression as attributes, but don't use
them for comparisons.

1 files changed, 8 insertions, 2 deletions

diff --git a/docs/django.rst b/docs/django.rst
index a43c3ed..ab98e67 100644
--- a/docs/django.rst
+++ b/docs/django.rst
@@ -6,7 +6,7 @@ Interaction with Django
 The ``python-semanticversion`` package provides two custom fields for Django:
 
 - :class:`VersionField`: stores a :class:`semantic_version.Version` object
-- :class:`SpecField`: stores a :class:`semantic_version.Spec` object
+- :class:`SpecField`: stores a :class:`semantic_version.BaseSpec` object
 
 Those fields are :class:`django.db.models.CharField` subclasses,
 with their :attr:`~django.db.models.CharField.max_length` defaulting to 200.
@@ -28,4 +28,10 @@ with their :attr:`~django.db.models.CharField.max_length` defaulting to 200.
 
 .. class:: SpecField
 
-    Stores a :class:`semantic_version.Spec` as its comma-separated string representation.
+    Stores a :class:`semantic_version.BaseSpec` as its textual representation.
+
+    .. attribute:: syntax
+
+        The syntax to use for the field; defaults to ``'native'``.
+
+        .. versionaddedd:: 2.7