Handle X ranges properly in includePrelease mode

Append a `-0` prerelease tag on the parsed comparators when in
includePrerelease mode.  Otherwise, 2.x will be satisfied by 3.0.0-beta,
since it's in `>=2.0.0 <3.0.0`.  However, `2.0.0-beta` will _not_
satisfy this range.

By appending the `-0`, the version set is pinned to the appropriate
boundary.

Note that doing this in non-prerelease-including mode would be a
mistake!  Appending the `-0` to the comparator means that prereleases in
the tuple are allowed, so `2.0.0-beta` would match `2.x` in
non-prerelease-including mode as well.  However, if we're including
prereleases, then their inclusion is intentional.

Fix: #282

semver.js

@@ -1208,11 +1208,12 @@ function replaceXRange (comp, options) {
         }
       }
 
-      ret = gtlt + M + '.' + m + '.' + p
+      ret = gtlt + M + '.' + m + '.' + p + pr
     } else if (xm) {
-      ret = '>=' + M + '.0.0 <' + (+M + 1) + '.0.0'
+      ret = '>=' + M + '.0.0' + pr + ' <' + (+M + 1) + '.0.0' + pr
     } else if (xp) {
-      ret = '>=' + M + '.' + m + '.0 <' + M + '.' + (+m + 1) + '.0'
+      ret = '>=' + M + '.' + m + '.0' + pr +
+        ' <' + M + '.' + (+m + 1) + '.0' + pr
     }
 
     debug('xRange return', ret)

test/index.js

@@ -249,11 +249,13 @@ test('range tests', function (t) {
     ['1.0.0 - x', '1.9.7'],
     ['1.x - x', '1.9.7'],
     ['<=7.x', '7.9.9'],
+    ['2.x', '2.0.0-pre.0', { includePrerelease: true }],
+    ['2.x', '2.1.0-pre.0', { includePrerelease: true }],
   ].forEach(function (v) {
     var range = v[0]
     var ver = v[1]
-    var loose = v[2]
-    t.ok(satisfies(ver, range, loose), range + ' satisfied by ' + ver)
+    var options = v[2]
+    t.ok(satisfies(ver, range, options), range + ' satisfied by ' + ver)
   })
   t.end()
 })
@@ -338,11 +340,12 @@ test('negative range tests', function (t) {
     // invalid versions never satisfy, but shouldn't throw
     ['*', 'not a version'],
     ['>=2', 'glorp'],
+    ['2.x', '3.0.0-pre.0', { includePrerelease: true }],
   ].forEach(function (v) {
     var range = v[0]
     var ver = v[1]
-    var loose = v[2]
-    var found = satisfies(ver, range, loose)
+    var options = v[2]
+    var found = satisfies(ver, range, options)
     t.ok(!found, ver + ' not satisfied by ' + range)
   })
   t.end()