Add some friendlier printing to the travis log for clang-format failures

.travis.yml

@@ -36,8 +36,6 @@ install:
   - if [[ "$DOCS_BUILD" == "1" ]]; then . ./scripts/travis/docs_setup.sh ; fi
   - if [[ "$TRAVIS_OS_NAME" == "linux" ]] && [[ "$CODE_BUILD" == "1" ]]; then . ./scripts/travis/linux_setup.sh ; fi
   - if [[ "$TRAVIS_OS_NAME" == "osx" ]] && [[ "$CODE_BUILD" == "1" ]]; then . ./scripts/travis/osx_setup.sh ; fi
-  - git clean -f
-  - git diff --exit-code
 
 script:
   - if [[ "$DOCS_BUILD" == "1" ]]; then . ./scripts/travis/docs_compile.sh ; fi

scripts/travis/linux_setup.sh

@@ -8,4 +8,25 @@ wget -O - http://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
 sudo apt-get update -qq 
 sudo apt-get install --allow-unauthenticated -y -qq libx11-dev mesa-common-dev libgl1-mesa-dev qt56base qt56x11extras libxcb-keysyms1-dev gdb clang-format-3.8
 
+# check formatting matches clang-format-3.8. Since newer versions can have
+# changes in formatting even without any rule changes, we have to fix on a
+# single version.
+
 clang-format-3.8 -i -style=file $(find pdblocate/ qrenderdoc/ renderdoc/ renderdoccmd/ renderdocshim/ -type f -regex '.*\(/3rdparty/\|/official/\|resource.h\).*' -prune -o -regex '.*\.\(c\|cpp\|h\)$' -print)
+
+git clean -f
+
+# this swallows the exit code so we won't fail until we print the diff in
+# the next line, but allows us to print a friendlier message to anyone
+# looking at the build log
+git diff --quiet || (
+  echo "***************************************************";
+  echo "*** The code is not clean against clang-format  ***";
+  echo "*** Please run clang-format-3.8 and fix the     ***";
+  echo "*** differences then rebase/squash them into    ***";
+  echo "*** the relevant commits. Do not add a commit   ***";
+  echo "*** for just formatting fixes. Thanks!          ***";
+  echo "***************************************************";
+  )
+
+git diff --exit-code