put up a note why `version-file-read` is tricky

libexec/rbenv-version-file-read

@@ -5,8 +5,8 @@ set -e
 VERSION_FILE="$1"
 
 if [ -e "$VERSION_FILE" ]; then
-  # Read and print the first non-whitespace word from the specified
-  # version file.
+  # Read the first non-whitespace word from the specified version file.
+  # Be careful not to load it whole in case there's something crazy in it.
   version=""
   while read -a words; do
     word="${words[0]}"