Accept single version interval syntax

Fixes https://github.com/alexarchambault/coursier/issues/310

core/shared/src/main/scala/coursier/core/Parse.scala

@@ -29,17 +29,32 @@ object Parse {
       None
 
   def versionInterval(s: String): Option[VersionInterval] = {
+
+    def parseBounds(fromIncluded: Boolean, toIncluded: Boolean, s: String) = {
+
+      val commaIdx = s.indexOf(',')
+
+      if (commaIdx >= 0) {
+        val strFrom = s.take(commaIdx)
+        val strTo = s.drop(commaIdx + 1)
+
+        for {
+          from <- if (strFrom.isEmpty) Some(None) else version(strFrom).map(Some(_))
+          to <- if (strTo.isEmpty) Some(None) else version(strTo).map(Some(_))
+        } yield VersionInterval(from.filterNot(_.isEmpty), to.filterNot(_.isEmpty), fromIncluded, toIncluded)
+      } else if (s.nonEmpty && fromIncluded && toIncluded)
+        for (v <- version(s) if !v.isEmpty)
+          yield VersionInterval(Some(v), Some(v), fromIncluded, toIncluded)
+      else
+        None
+    }
+
     for {
       fromIncluded <- if (s.startsWith("[")) Some(true) else if (s.startsWith("(")) Some(false) else None
       toIncluded <- if (s.endsWith("]")) Some(true) else if (s.endsWith(")")) Some(false) else None
       s0 = s.drop(1).dropRight(1)
-      commaIdx = s0.indexOf(',')
-      if commaIdx >= 0
-      strFrom = s0.take(commaIdx)
-      strTo = s0.drop(commaIdx + 1)
-      from <- if (strFrom.isEmpty) Some(None) else version(strFrom).map(Some(_))
-      to <- if (strTo.isEmpty) Some(None) else version(strTo).map(Some(_))
-    } yield VersionInterval(from.filterNot(_.isEmpty), to.filterNot(_.isEmpty), fromIncluded, toIncluded)
+      itv <- parseBounds(fromIncluded, toIncluded, s0)
+    } yield itv
   }
 
   def versionConstraint(s: String): Option[VersionConstraint] = {

tests/shared/src/test/resources/resolutions/io.grpc/grpc-netty/0.14.1

@@ -0,0 +1,12 @@
+com.google.code.findbugs:jsr305:3.0.0:compile
+com.google.guava:guava:19.0:compile
+io.grpc:grpc-core:0.14.1:compile
+io.grpc:grpc-netty:0.14.1:compile
+io.netty:netty-buffer:4.1.1.Final:compile
+io.netty:netty-codec:4.1.1.Final:compile
+io.netty:netty-codec-http:4.1.1.Final:compile
+io.netty:netty-codec-http2:4.1.1.Final:compile
+io.netty:netty-common:4.1.1.Final:compile
+io.netty:netty-handler:4.1.1.Final:compile
+io.netty:netty-resolver:4.1.1.Final:compile
+io.netty:netty-transport:4.1.1.Final:compile

tests/shared/src/test/scala/coursier/test/CentralTests.scala

@@ -280,6 +280,13 @@ object CentralTests extends TestSuite {
       }
     }
 
+    'fixedVersionDependency - {
+      val mod = Module("io.grpc", "grpc-netty")
+      val version = "0.14.1"
+
+      resolutionCheck(mod, version)
+    }
+
     'mavenScopes - {
       def check(config: String) = resolutionCheck(
         Module("com.android.tools", "sdklib"),

tests/shared/src/test/scala/coursier/test/VersionIntervalTests.scala

@@ -163,10 +163,6 @@ object VersionIntervalTests extends TestSuite {
 
     'parse{
       'malformed{
-        val s1 = "[1.1]"
-        val itv1 = Parse.versionInterval(s1)
-        assert(itv1 == None)
-
         val s2 = "(1.1)"
         val itv2 = Parse.versionInterval(s2)
         assert(itv2 == None)
@@ -263,6 +259,38 @@ object VersionIntervalTests extends TestSuite {
         assert(itv4 == Some(VersionInterval(None, None, false, true)))
         assert(!itv4.get.isValid)
       }
+
+      'fixedVersion - {
+        * - {
+          val itv = Parse.versionInterval("[1.2]")
+          assert(itv == Some(VersionInterval(Some(Version("1.2")), Some(Version("1.2")), true, true)))
+        }
+
+        * - {
+          val itv = Parse.versionInterval("[1.2)")
+          assert(itv.isEmpty)
+        }
+
+        * - {
+          val itv = Parse.versionInterval("(1.2]")
+          assert(itv.isEmpty)
+        }
+
+        * - {
+          val itv = Parse.versionInterval("(1.2)")
+          assert(itv.isEmpty)
+        }
+
+        * - {
+          val itv = Parse.versionInterval("[]")
+          assert(itv.isEmpty)
+        }
+
+        * - {
+          val itv = Parse.versionInterval("[0.0]")
+          assert(itv.isEmpty)
+        }
+      }
     }
 
     'constraint{