travis: macOS is optional

.travis.yml

@@ -9,7 +9,7 @@ env:
 # Default --recursive (rapidjson/thirdparty/gtest) is unnecessary
 git:
   submodules: false
-  depth: 3
+  depth: 1
 
 before_install:
   - git submodule update --init
@@ -19,11 +19,6 @@ addons:
     sources: &apt_sources
       - ubuntu-toolchain-r-test
       - llvm-toolchain-precise-3.5
-      #- llvm-toolchain-precise-3.6
-      #- llvm-toolchain-precise-3.7
-      #- llvm-toolchain-precise-3.8
-      #- llvm-toolchain-trusty-3.9
-      #- llvm-toolchain-trusty-4.0
       - llvm-toolchain-trusty-5.0
 
 compiler: clang
@@ -44,13 +39,6 @@ matrix:
           packages: ["g++-5"]
           sources: *apt_sources
 
-    # - env: COMPILER=g++-6
-    #   compiler: gcc
-    #   addons: &gcc6
-    #     apt:
-    #       packages: ["g++-6"]
-    #       sources: *apt_sources
-
     - env: COMPILER=g++-7
       compiler: gcc
       addons: &gcc7
@@ -64,91 +52,37 @@ matrix:
           packages: ["clang-3.5", "g++-7"]
           sources: *apt_sources
 
-    # - env: COMPILER=clang++-3.6
-    #   addons: &clang36
-    #     apt:
-    #       packages: ["clang-3.6", "g++-7"]
-    #       sources: *apt_sources
-
-    # - env: COMPILER=clang++-3.7
-    #   addons: &clang37
-    #     apt:
-    #       packages: ["clang-3.7", "g++-7"]
-    #       sources: *apt_sources
-
-    # - env: COMPILER=clang++-3.8
-    #   addons: &clang38
-    #     apt:
-    #       packages: ["clang-3.8", "g++-7"]
-    #       sources: *apt_sources
-
-    # - env: COMPILER=clang++-3.9
-    #   addons: &clang39
-    #     apt:
-    #       packages: ["clang-3.9", "g++-7"]
-    #       sources: *apt_sources
-
-    # - env: COMPILER=clang++-4.0
-    #   addons: &clang40
-    #     apt:
-    #       packages: ["clang-4.0", "g++-7"]
-    #       sources: *apt_sources
-
     - env: COMPILER=clang++-5.0
       addons: &clang50
         apt:
           packages: ["clang-5.0", "g++-7"]
           sources: *apt_sources
 
-    # - env: COMPILER=clang++
-    #   osx_image: xcode6.4
-    #   os: osx
-
-    # - env: COMPILER=clang++
-    #   osx_image: xcode7.3
-    #   os: osx
-
-    # - env: COMPILER=clang++
-    #   osx_image: xcode8
-    #   os: osx
-
-    # - env: COMPILER=clang++
-    #   osx_image: xcode8.1
-    #   os: osx
-
-    # - env: COMPILER=clang++
-    #   osx_image: xcode8.2
-    #   os: osx
-
-    # - env: COMPILER=clang++
-    #   osx_image: xcode8.3
-    #   os: osx
-
-    # - env: COMPILER=clang++
-    #   osx_image: xcode9
-    #   os: osx
-
     - env: COMPILER=clang++
       osx_image: xcode9.1
       os: osx
 
-    # - env: COMPILER=g++-5
-    #   compiler: gcc
-    #   osx_image: xcode9.1
-    #   os: osx
-
-    # - env: COMPILER=g++-6
-    #   compiler: gcc
-    #   osx_image: xcode9.1
-    #   os: osx
-
     - env: COMPILER=g++-7
       compiler: gcc
       osx_image: xcode9.1
       os: osx
 
+
   allow_failures:
 
+    # macOS takes too long.
+
+    - env: COMPILER=clang++
+      osx_image: xcode9.1
+      os: osx
+
+    - env: COMPILER=g++-7
+      compiler: gcc
+      osx_image: xcode9.1
+      os: osx
+
+    # gcc builds that should be fixed at some point
+
     - env: COMPILER=g++-5
       compiler: gcc