Restore style checking on travis (#3080)

Author: paulb777

.travis.yml

@@ -17,7 +17,7 @@ jobs:
         - brew install clang-format
         - brew install swiftformat
       script:
-        - ./scripts/check.sh --test-only $TRAVIS_COMMIT_RANGE
+        - ./scripts/check.sh --test-only
 
     # The order of builds matters (even though they are run in parallel):
     # Travis will schedule them in the same order they are listed here.

scripts/check.sh

@@ -93,6 +93,20 @@ if [[ ! -t 1 ]]; then
   VERBOSE=true
 fi
 
+# When travis clones a repo for building, it uses a shallow clone. After the
+# first commit on a non-master branch, TRAVIS_COMMIT_RANGE is not set, master
+# is not available and we need to compute the START_REVISION from the common
+# ancestor of $TRAVIS_COMMIT and origin/master.
+if [[ -n "${TRAVIS_COMMIT_RANGE:-}" ]] ; then
+  START_REVISION="$TRAVIS_COMMIT_RANGE"
+elif [[ -n "${TRAVIS_COMMIT:-}" ]] ; then
+  if ! git rev-parse origin/master >& /dev/null; then
+    git remote set-branches --add origin master
+    git fetch origin
+  fi
+  START_REVISION=$(git merge-base origin/master "${TRAVIS_COMMIT}")
+fi
+
 while [[ $# -gt 0 ]]; do
   case "$1" in
     --)
@@ -163,19 +177,23 @@ if [[ "${VERBOSE}" == true ]]; then
   env | egrep '^TRAVIS_(BRANCH|COMMIT|PULL|REPO)' | sort || true
 fi
 
-# When travis clones a repo for building, it uses a shallow clone. After the
-# first commit on a non-master branch, TRAVIS_COMMIT_RANGE is not set and
-# START_REVISION is "master" instead of a range.
+if [[ "${START_REVISION}" == *..* ]]; then
+  RANGE_START="${START_REVISION/..*/}"
+  RANGE_END="${START_REVISION/*../}"
 
-# If needed, check if we have access to master and add it to the repo.
-if [[ "${START_REVISION}" == "origin/master" ]]; then
+  # Figure out if we have access to master. If not add it to the repo.
   if ! git rev-parse origin/master >& /dev/null; then
     git remote set-branches --add origin master
     git fetch origin
   fi
-fi
 
-START_SHA=$(git rev-parse "${START_REVISION}")
+  NEW_RANGE_START=$(git merge-base origin/master "${RANGE_END}")
+  START_REVISION="${START_REVISION/$RANGE_START/$NEW_RANGE_START}"
+  START_SHA="${START_REVISION}"
+
+else
+  START_SHA=$(git rev-parse "${START_REVISION}")
+fi
 
 if [[ "${VERBOSE}" == true ]]; then
   echo "START_REVISION=$START_REVISION"