Incorporate lessons learned from latest publishing. (#693)

* Drop pomExtra scm definitions (now generated by git.remoteRepo.

* Incorporate lessons learned from latest publishing.

build.sbt

@@ -57,12 +57,11 @@ lazy val commonSettings = Seq (
   }
 )
 
-lazy val chiselSettings = Seq (
-  name := "chisel3",
-
+lazy val publishSettings = Seq (
   publishMavenStyle := true,
   publishArtifact in Test := false,
   pomIncludeRepository := { x => false },
+  // Don't add 'scm' elements if we have a git.remoteRepo definition.
   pomExtra := <url>http://chisel.eecs.berkeley.edu/</url>
     <licenses>
       <license>
@@ -71,10 +70,6 @@ lazy val chiselSettings = Seq (
         <distribution>repo</distribution>
       </license>
     </licenses>
-    <scm>
-      <url>https://github.com/freechipsproject/chisel3.git</url>
-      <connection>scm:git:github.com/freechipsproject/chisel3.git</connection>
-    </scm>
     <developers>
       <developer>
         <id>jackbackrack</id>
@@ -92,12 +87,11 @@ lazy val chiselSettings = Seq (
     else {
       Some("releases" at nexus + "service/local/staging/deploy/maven2")
     }
-  },
+  }
+)
 
-  resolvers ++= Seq(
-    Resolver.sonatypeRepo("snapshots"),
-    Resolver.sonatypeRepo("releases")
-  ),
+lazy val chiselSettings = Seq (
+  name := "chisel3",
 
   libraryDependencies ++= Seq(
     "org.scalatest" %% "scalatest" % "3.0.1" % "test",
@@ -133,6 +127,7 @@ lazy val chisel = (project in file(".")).
   ).
   settings(commonSettings: _*).
   settings(chiselSettings: _*).
+  settings(publishSettings: _*).
   // Prevent separate JARs from being generated for coreMacros and chiselFrontend.
   dependsOn(coreMacros % "compile-internal;test-internal").
   dependsOn(chiselFrontend % "compile-internal;test-internal").