config: Improve the Provider matching to have a negated match #2140

This makes it easier to make classes of provider in the config.

fs/config/config_test.go

@@ -1,6 +1,7 @@
 package config
 
 import (
+	"fmt"
 	"io/ioutil"
 	"os"
 	"testing"
@@ -205,3 +206,24 @@ func hashedKeyCompare(t *testing.T, a, b string, shouldMatch bool) {
 		assert.NotEqual(t, k1, k2)
 	}
 }
+
+func TestMatchProvider(t *testing.T) {
+	for _, test := range []struct {
+		config   string
+		provider string
+		want     bool
+	}{
+		{"", "", true},
+		{"one", "one", true},
+		{"one,two", "two", true},
+		{"one,two,three", "two", true},
+		{"one", "on", false},
+		{"one,two,three", "tw", false},
+		{"!one,two,three", "two", false},
+		{"!one,two,three", "four", true},
+	} {
+		what := fmt.Sprintf("%q,%q", test.config, test.provider)
+		got := matchProvider(test.config, test.provider)
+		assert.Equal(t, test.want, got, what)
+	}
+}