4 files changed, 62 insertions, 4 deletions
diff --git a/config/configLoader.go b/config/configLoader.go
index b8aa3fda3..2e37a5b35 100644
--- a/config/configLoader.go
+++ b/config/configLoader.go
@@ -120,8 +120,6 @@ func RenameKeys(m map[string]interface{}) {
 
 func newViper() *viper.Viper {
 	v := viper.New()
-	v.AutomaticEnv()
-	v.SetEnvPrefix("hugo")
 
 	return v
 }
diff --git a/config/configProvider.go b/config/configProvider.go
index 31914c38b..187fb7b10 100644
--- a/config/configProvider.go
+++ b/config/configProvider.go
@@ -35,10 +35,14 @@ type Provider interface {
 // we do not attempt to split it into fields.
 func GetStringSlicePreserveString(cfg Provider, key string) []string {
 	sd := cfg.Get(key)
-	if sds, ok := sd.(string); ok {
+	return toStringSlicePreserveString(sd)
+}
+
+func toStringSlicePreserveString(v interface{}) []string {
+	if sds, ok := v.(string); ok {
 		return []string{sds}
 	}
-	return cast.ToStringSlice(sd)
+	return cast.ToStringSlice(v)
 }
 
 // SetBaseTestDefaults provides some common config defaults used in tests.
diff --git a/config/env.go b/config/env.go
index adf6f9b68..f482cd247 100644
--- a/config/env.go
+++ b/config/env.go
@@ -17,6 +17,7 @@ import (
 	"os"
 	"runtime"
 	"strconv"
+	"strings"
 )
 
 // GetNumWorkerMultiplier returns the base value used to calculate the number
@@ -31,3 +32,26 @@ func GetNumWorkerMultiplier() int {
 	}
 	return runtime.NumCPU()
 }
+
+// SetEnvVars sets vars on the form key=value in the oldVars slice.
+func SetEnvVars(oldVars *[]string, keyValues ...string) {
+	for i := 0; i < len(keyValues); i += 2 {
+		setEnvVar(oldVars, keyValues[i], keyValues[i+1])
+	}
+}
+
+func SplitEnvVar(v string) (string, string) {
+	parts := strings.Split(v, "=")
+	return parts[0], parts[1]
+}
+
+func setEnvVar(vars *[]string, key, value string) {
+	for i := range *vars {
+		if strings.HasPrefix((*vars)[i], key+"=") {
+			(*vars)[i] = key + "=" + value
+			return
+		}
+	}
+	// New var.
+	*vars = append(*vars, key+"="+value)
+}
diff --git a/config/env_test.go b/config/env_test.go
new file mode 100644
index 000000000..594c3e871
--- /dev/null
+++ b/config/env_test.go
@@ -0,0 +1,32 @@
+// Copyright 2019 The Hugo Authors. All rights reserved.
+//
+// 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 config
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestSetEnvVars(t *testing.T) {
+	t.Parallel()
+	assert := require.New(t)
+	vars := []string{"FOO=bar", "HUGO=cool", "BAR=foo"}
+	SetEnvVars(&vars, "HUGO", "rocking!", "NEW", "bar")
+	assert.Equal([]string{"FOO=bar", "HUGO=rocking!", "BAR=foo", "NEW=bar"}, vars)
+
+	key, val := SplitEnvVar("HUGO=rocks")
+	assert.Equal("HUGO", key)
+	assert.Equal("rocks", val)
+}