Change grep to not require include support and suppress error on lack…

… of tf files

libexec/tfenv-min-required

@@ -74,7 +74,7 @@ see https://www.terraform.io/docs/configuration/terraform.html for details';
 find_min_required() {
   local root="${1}";
 
-  versions="$( echo $(grep -h required_version --include '*tf' "${root}"/* ) | grep  -o '\([0-9]\+\.\?\)\{2,3\}\(-[a-z]\+[0-9]\+\)\?')";
+  versions="$( echo $(grep -h required_version "${root}"/*.tf 2>/dev/null ) | grep  -o '\([0-9]\+\.\?\)\{2,3\}\(-[a-z]\+[0-9]\+\)\?')";
 
   if [[ "${versions}" =~ ([~=!<>]{0,2}[[:blank:]]*[0-9]+[0-9.]+)[^0-9]*(-[a-z]+[0-9]+)? ]]; then
     found_min_required="${BASH_REMATCH[1]}${BASH_REMATCH[2]}"