pkg/osutil: add Unsetenv

go1.4 doesn't support static link well, so we stay in go1.3 for a while.
Implement Unsetenv in go1.3 way.

pkg/osutil/osutil_test.go

@@ -0,0 +1,45 @@
+// Copyright 2015 CoreOS, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package osutil
+
+import (
+	"os"
+	"reflect"
+	"testing"
+)
+
+func TestUnsetenv(t *testing.T) {
+	tests := []string{
+		"data",
+		"space data",
+		"equal=data",
+	}
+	for i, tt := range tests {
+		key := "ETCD_UNSETENV_TEST"
+		if os.Getenv(key) != "" {
+			t.Fatalf("#%d: cannot get empty %s", i, key)
+		}
+		env := os.Environ()
+		if err := os.Setenv(key, tt); err != nil {
+			t.Fatalf("#%d: cannot set %s: %v", i, key, err)
+		}
+		if err := Unsetenv(key); err != nil {
+			t.Errorf("#%d: unsetenv %s error: %v", i, key, err)
+		}
+		if g := os.Environ(); !reflect.DeepEqual(g, env) {
+			t.Errorf("#%d: env = %+v, want %+v", i, g, env)
+		}
+	}
+}