Add alpine support in univers

Currently univers don't have a VersionClass for alpine linux, so add a version class for alpine linux and use same vercmp method that has been used by gentoo, avoid cases for now  which have a leading 0 in them.

Verify the current implementation of vercmp with the test data from here https://git.alpinelinux.org/apk-tools/tree/tests/version.data addABOUT file and license for same

Signed-off-by: Tushar Goel <tushar.goel.dav@gmail.com>

Author: TG1999

src/univers/debian.py

@@ -256,7 +256,9 @@ def compare_strings(version1, version2):
             logger.debug("Comparing non-digit prefixes %r and %r ..", p1, p2)
             for c1, c2 in zip_longest(p1, p2, fillvalue=""):
                 logger.debug(
-                    "Performing lexical comparison between characters %r and %r ..", c1, c2
+                    "Performing lexical comparison between characters %r and %r ..",
+                    c1,
+                    c2,
                 )
                 o1 = mapping.get(c1)
                 o2 = mapping.get(c2)

src/univers/version_range.py

@@ -721,6 +721,11 @@ class EbuildVersionRange(VersionRange):
     version_class = versions.GentooVersion
 
 
+class AlpineLinuxVersionRange(VersionRange):
+    scheme = "alpinelinux"
+    version_class = versions.AlpineLinuxVersion
+
+
 class ArchLinuxVersionRange(VersionRange):
     scheme = "archlinux"
     version_class = versions.ArchLinuxVersion

src/univers/versions.py

@@ -34,6 +34,14 @@ class InvalidVersion(ValueError):
     pass
 
 
+def valid_alpine_version(s):
+    left, _, _ = s.partition(".")
+    if not left.isdigit():
+        return True
+    i = int(left)
+    return str(i) == left
+
+
 @attr.s(frozen=True, order=False, hash=True)
 class Version:
     """
@@ -299,3 +307,25 @@ def __lt__(self, other):
         if not isinstance(other, self.__class__):
             return NotImplemented
         return gentoo.vercmp(self.value, other.value) == -1
+
+
+@attr.s(frozen=True, order=False, eq=False, hash=True)
+class AlpineLinuxVersion(Version):
+    @classmethod
+    def is_valid(cls, string):
+        return valid_alpine_version(string) and gentoo.is_valid(string)
+
+    def __eq__(self, other):
+        if not isinstance(other, self.__class__):
+            return NotImplemented
+        return gentoo.vercmp(self.value, other.value) == 0
+
+    def __lt__(self, other):
+        if not isinstance(other, self.__class__):
+            return NotImplemented
+        return gentoo.vercmp(self.value, other.value) < 0
+
+    def __gt__(self, other):
+        if not isinstance(other, self.__class__):
+            return NotImplemented
+        return gentoo.vercmp(self.value, other.value) > 0