Commit updated PDF.js build as part of tools/update-pdfjs

This serves to standardize how PDF.js updates are committed in the
repository.

Author: robertknight

tools/update-pdfjs

@@ -17,6 +17,14 @@ DEST_DIR=src/vendor/pdfjs
 PREFIX=pdf.js-gh-pages
 COMPONENTS="$PREFIX/build $PREFIX/web $PREFIX/LICENSE"
 
+# Check for uncommitted git changes. See https://stackoverflow.com/a/3879077/434243
+git update-index --refresh
+git diff-index --quiet HEAD --
+if [[ $? -ne 0 ]]; then
+  echo "Cannot update PDF.js when there are uncommitted changes in working tree."
+  exit 1
+fi
+
 # Download the latest version of the PDF.js library and viewer.
 rm -rf $DEST_DIR
 mkdir -p $DEST_DIR
@@ -45,3 +53,11 @@ cat <<END > src/vendor/pdfjs/HYPOTHESIS-README.md
 
 This is a build of the PDF.js viewer auto-generated by tools/update-pdfjs.
 END
+
+# Look for `const pdfjsVersion = '<VERSION>'` line in source and extract VERSION.
+PDFJS_VERSION=$(grep pdfjsVersion src/vendor/pdfjs/web/viewer.js | egrep -o '[0-9.]+')
+git add src/vendor/pdfjs
+git commit -m "Update PDF.js to v$PDFJS_VERSION
+
+Update PDF.js using $0."
+