fix git range to be usable locally

Author: mark-i-m

ci/linkcheck.sh

@@ -1,14 +1,14 @@
 #!/usr/bin/env bash
 
 if [ "$TRAVIS_EVENT_TYPE" = "cron" ] ; then
-  echo "Doing full link check."
   FLAGS=""
-else
-  echo "Checking files changed in commit range: $TRAVIS_COMMIT_RANGE"
-  CHANGED_FILES=$(git diff-tree --no-commit-id --name-only -r $TRAVIS_COMMIT_RANGE | tr '\n' ' ')
 
-  echo "Checking only changed files: $CHANGED_FILES"
+  echo "Doing full link check."
+else
+  CHANGED_FILES=$(git diff-tree --no-commit-id --name-only -r master..HEAD | tr '\n' ' ')
   FLAGS="-f $CHANGED_FILES"
+
+  echo "Checking files changed in master..HEAD: $CHANGED_FILES"
 fi
 
 exec mdbook-linkcheck $FLAGS -- $TRAVIS_BUILD_DIR