v2 Passing all tests

README.md

@@ -33,53 +33,37 @@ As a command-line utility:
 
 ## Versions
 
-A version is the following things, in this order:
-
-* a number (Major)
-* a period
-* a number (minor)
-* a period
-* a number (patch)
-* OPTIONAL: a hyphen, followed by a number (build)
-* OPTIONAL: a collection of pretty much any non-whitespace characters
-  (tag)
+A "version" is described by the v2.0.0 specification found at
+<http://semver.org/>.
 
 A leading `"="` or `"v"` character is stripped off and ignored.
 
-## Comparisons
-
-The ordering of versions is done using the following algorithm, given
-two versions and asked to find the greater of the two:
-
-* If the majors are numerically different, then take the one
-  with a bigger major number. `2.3.4 > 1.3.4`
-* If the minors are numerically different, then take the one
-  with the bigger minor number. `2.3.4 > 2.2.4`
-* If the patches are numerically different, then take the one with the
-  bigger patch number. `2.3.4 > 2.3.3`
-* If only one of them has a build number, then take the one with the
-  build number.  `2.3.4-0 > 2.3.4`
-* If they both have build numbers, and the build numbers are numerically
-  different, then take the one with the bigger build number.
-  `2.3.4-10 > 2.3.4-9`
-* If only one of them has a tag, then take the one without the tag.
-  `2.3.4 > 2.3.4-beta`
-* If they both have tags, then take the one with the lexicographically
-  larger tag.  `2.3.4-beta > 2.3.4-alpha`
-* At this point, they're equal.
-
 ## Ranges
 
 The following range styles are supported:
 
+* `1.2.3` A specific version.  When nothing else will do.  Note that
+  build metadata is still ignored, so `1.2.3+build2012` will satisfy
+  this range.
 * `>1.2.3` Greater than a specific version.
-* `<1.2.3` Less than
-* `1.2.3 - 2.3.4` := `>=1.2.3 <=2.3.4`
-* `~1.2.3` := `>=1.2.3 <1.3.0`
-* `~1.2` := `>=1.2.0 <1.3.0`
-* `~1` := `>=1.0.0 <2.0.0`
-* `1.2.x` := `>=1.2.0 <1.3.0`
-* `1.x` := `>=1.0.0 <2.0.0`
+* `<1.2.3` Less than a specific version.  If there is no prerelease
+  tag on the version range, then no prerelease version will be allowed
+  either, even though these are technically "less than".
+* `>=1.2.3` Greater than or equal to.  Note that prerelease versions
+  are NOT equal to their "normal" equivalents, so `1.2.3-beta` will
+  not satisfy this range, but `2.3.0-beta` will.
+* `<=1.2.3` Less than or equal to.  In this case, prerelease versions
+  ARE allowed, so `1.2.3-beta` would satisfy.
+* `1.2.3 - 2.3.4` := `>=1.2.3-0 <=2.3.4-0`
+* `~1.2.3` := `>=1.2.3-0 <1.3.0-0`  "Reasonably close to 1.2.3".  When
+  using tilde operators, prerelease versions are supported as well,
+  but a prerelease of the next significant digit will NOT be
+  satisfactory, so `1.3.0-beta` will not satisfy `~1.2.3`.
+* `~1.2` := `>=1.2.0-0 <1.3.0-0` "Any version starting with 1.2"
+* `1.2.x` := `>=1.2.0-0 <1.3.0-0` "Any version starting with 1.2"
+* `~1` := `>=1.0.0-0 <2.0.0-0` "Any version starting with 1"
+* `1.x` := `>=1.0.0-0 <2.0.0-0` "Any version starting with 1"
+
 
 Ranges can be joined with either a space (which implies "and") or a
 `||` (which implies "or").