redo how crossScalaVersions works

the old scheme was: run tests on openjdk7, but only publish (for all
Scala versions) from openjdk6

this is no longer appropriate now that Scala 2.12.0-M2 requires Java 8.
now we want to publish for older Scala versions using openjdk6, but
newer versions (M2 and above) using openjdk8. this commit does that.

what happened to running tests on openjdk7?  well, neither Lukas nor I
knows why it was even doing that.

Author: SethTisue

.travis.yml

@@ -5,7 +5,6 @@ language: scala
 
 env:
   global:
-    - PUBLISH_JDK=openjdk6
     # PGP_PASSPHRASE
     - secure: "XLe/gZXrGwJlKCgAUoEUIHwoh8js0IdlIazwUd5KKssZMQkPg4VfC5LLPl8iXCYIRe2JrgmD56b7eseiZF9kMxa1Rsz8fSMY0v3A0qwxRjbsxVQ2NqEvdq+TNOAhjo/OmPnipvTcDdAyq68Ca4nTSBtfBpy5t6X3Z4UIl8CWLdw="
     # SONA_USER
@@ -17,7 +16,7 @@ script: admin/build.sh
 
 jdk:
   - openjdk6
-  - openjdk7
+  - openjdk8
 
 notifications:
   email: [email protected]

admin/README.md

@@ -19,7 +19,8 @@ To configure tag driven releases from Travis CI.
      Edit `.travis.yml` as prompted.
   4. Edit `.travis.yml` to use `./admin/build.sh` as the build script,
      and edit that script to use the tasks required for this project.
-  5. Edit `.travis.yml` to select which JDK will be used for publishing.
+  5. Edit `build.sbt` to select which JDK will be used for publishing
+     for which Scala versions.
 
 It is important to add comments in .travis.yml to identify the name
 of each environment variable encoded in a `:secure` section.
@@ -30,7 +31,6 @@ form:
 	language: scala
 	env:
 	  global:
-	    - PUBLISH_JDK=openjdk6
 	    # PGP_PASSPHRASE
 	    - secure: "XXXXXX"
 	    # SONA_USER
@@ -58,4 +58,3 @@ Be sure to use SBT 0.13.7 or higher to avoid [#1430](https://github.com/sbt/sbt/
   3. Log into https://oss.sonatype.org/ and identify the staging repository.
   4. Sanity check its contents
   5. Release staging repository to Maven and send out release announcement.
-

admin/build.sh

@@ -7,7 +7,7 @@ set -e
 # git on travis does not fetch tags, but we have TRAVIS_TAG
 # headTag=$(git describe --exact-match ||:)
 
-if [ "$TRAVIS_JDK_VERSION" == "$PUBLISH_JDK" ] && [[ "$TRAVIS_TAG" =~ ^v[0-9]+\.[0-9]+\.[0-9]+(-[A-Za-z0-9-]+)? ]]; then
+if [[ "$TRAVIS_TAG" =~ ^v[0-9]+\.[0-9]+\.[0-9]+(-[A-Za-z0-9-]+)? ]]; then
   echo "Going to release from tag $TRAVIS_TAG!"
   myVer=$(echo $TRAVIS_TAG | sed -e s/^v//)
   publishVersion='set every version := "'$myVer'"'

build.sbt

@@ -8,7 +8,15 @@ version                    := "1.0.9-SNAPSHOT"
 
 scalaVersion               := crossScalaVersions.value.head
 
-crossScalaVersions         := Seq("2.11.6", "2.12.0-M1")
+crossScalaVersions         := {
+  val java = System.getProperty("java.version")
+  if (java.startsWith("1.6."))
+    Seq("2.11.6", "2.12.0-M1")
+  else if (java.startsWith("1.8."))
+    Seq("2.12.0-M2")
+  else
+    sys.error(s"don't know what Scala versions to build on $java")
+}
 
 scalaXmlVersion            := "1.0.4"