lint: Don't use TRAVIS_COMMIT_RANGE in whitespace linter

test/lint/lint-whitespace.sh

@@ -13,32 +13,41 @@ while getopts "?" opt; do
   case $opt in
     ?)
       echo "Usage: $0 [N]"
-      echo "       TRAVIS_COMMIT_RANGE='<commit range>' $0"
+      echo "       COMMIT_RANGE='<commit range>' $0"
       echo "       $0 -?"
       echo "Checks unstaged changes, the previous N commits, or a commit range."
-      echo "TRAVIS_COMMIT_RANGE='47ba2c3...ee50c9e' $0"
+      echo "COMMIT_RANGE='47ba2c3...ee50c9e' $0"
       exit 0
     ;;
   esac
 done
 
-if [ -z "${TRAVIS_COMMIT_RANGE}" ]; then
+# TRAVIS_BRANCH will be present in a Travis environment. For builds triggered
+# by a pull request this is the name of the branch targeted by the pull request.
+# https://docs.travis-ci.com/user/environment-variables/
+if [ -n "${TRAVIS_BRANCH}" ]; then
+  COMMIT_RANGE="$TRAVIS_BRANCH..HEAD"
+fi
+
+if [ -z "${COMMIT_RANGE}" ]; then
   if [ -n "$1" ]; then
-    TRAVIS_COMMIT_RANGE="HEAD~$1...HEAD"
+    COMMIT_RANGE="HEAD~$1...HEAD"
   else
-    TRAVIS_COMMIT_RANGE="HEAD"
+    # This assumes that the target branch of the pull request will be master.
+    MERGE_BASE=$(git merge-base HEAD master)
+    COMMIT_RANGE="$MERGE_BASE..HEAD"
   fi
 fi
 
 showdiff() {
-  if ! git diff -U0 "${TRAVIS_COMMIT_RANGE}" -- "." ":(exclude)depends/patches/" ":(exclude)src/leveldb/" ":(exclude)src/crc32c/" ":(exclude)src/secp256k1/" ":(exclude)src/univalue/" ":(exclude)doc/release-notes/" ":(exclude)src/qt/locale/"; then
+  if ! git diff -U0 "${COMMIT_RANGE}" -- "." ":(exclude)depends/patches/" ":(exclude)src/leveldb/" ":(exclude)src/crc32c/" ":(exclude)src/secp256k1/" ":(exclude)src/univalue/" ":(exclude)doc/release-notes/" ":(exclude)src/qt/locale/"; then
     echo "Failed to get a diff"
     exit 1
   fi
 }
 
 showcodediff() {
-  if ! git diff -U0 "${TRAVIS_COMMIT_RANGE}" -- *.cpp *.h *.md *.py *.sh ":(exclude)src/leveldb/" ":(exclude)src/crc32c/" ":(exclude)src/secp256k1/" ":(exclude)src/univalue/" ":(exclude)doc/release-notes/" ":(exclude)src/qt/locale/"; then
+  if ! git diff -U0 "${COMMIT_RANGE}" -- *.cpp *.h *.md *.py *.sh ":(exclude)src/leveldb/" ":(exclude)src/crc32c/" ":(exclude)src/secp256k1/" ":(exclude)src/univalue/" ":(exclude)doc/release-notes/" ":(exclude)src/qt/locale/"; then
     echo "Failed to get a diff"
     exit 1
   fi