fix legacy CI test

Author: rhysd

.travis.yml

@@ -1,14 +1,24 @@
 language: ruby
+sudo: false
 rvm:
     - 1.9.3
-script: rake ci
+
 env:
-    - CLANG_VERSION="3.4"
-    - CLANG_VERSION="3.5"
+    - CLANG_VERSION="3.7"
+    - CLANG_VERSION="3.8"
+
 install:
-    - sudo sh -c "echo 'deb http://llvm.org/apt/precise/ llvm-toolchain-precise-${CLANG_VERSION} main' >> /etc/apt/sources.list"
-    - wget -O - http://llvm.org/apt/llvm-snapshot.gpg.key | sudo apt-key add -
-    - sudo apt-get -qq update
-    - sudo apt-get -qq --force-yes install clang-format-${CLANG_VERSION}
     - bundle install
     - clang-format-${CLANG_VERSION} -version || true
+
+script:
+    - CLANG_FORMAT=clang-format-${CLANG_VERSION} rake ci
+
+cache:
+    - apt
+
+addons:
+    apt:
+        packages:
+            - clang-format-3.8
+            - clang-format-3.7

t/clang_format_spec.vim

@@ -4,9 +4,14 @@
 " helpers "{{{
 " clang-format detection
 function! s:detect_clang_format()
-    for candidate in ['clang-format-3.4', 'clang-format', 'clang-format-HEAD', 'clang-format-3.5']
-        if executable(candidate)
-            return candidate
+    if $CLANG_FORMAT !=# '' && executable($CLANG_FORMAT)
+        return $CLANG_FORMAT
+    endif
+
+    for suffix in ['-HEAD', '-3.8', '-3.7', '-3.6', '-3.5', '-3.4', '']
+        let c = 'clang-format' . suffix
+        if executable(c)
+            return c
         endif
     endfor
     throw 'not ok because detect clang-format could not be found in $PATH'