commands: Support config from ENV

So

```bash
env HUGO_TITLE="Some Title" hugo server
```

Will change the `title`.

Fixes #2090

diff --git a/commands/hugo.go b/commands/hugo.go
index 7cb1a4fc365329361b7e8fbe129d83df5291e8ef..ec77047a23d29cfee11d6c425ec3f3657461852b 100644 (file)
--- a/commands/hugo.go
+++ b/commands/hugo.go
@@ -17,7 +17,6 @@ package commands
 
 import (
        "fmt"
-       "github.com/spf13/hugo/hugofs"
        "io/ioutil"
        "net/http"
        "os"
@@ -27,6 +26,8 @@ import (
        "sync"
        "time"
 
+       "github.com/spf13/hugo/hugofs"
+
        "github.com/spf13/hugo/parser"
        flag "github.com/spf13/pflag"
 
@@ -318,6 +319,8 @@ func loadDefaultSettings() {
 // A Hugo command that calls initCoreCommonFlags() can pass itself
 // as an argument to have its command-line flags processed here.
 func InitializeConfig(subCmdVs ...*cobra.Command) error {
+       viper.AutomaticEnv()
+       viper.SetEnvPrefix("hugo")
        viper.SetConfigFile(cfgFile)
        // See https://github.com/spf13/viper/issues/73#issuecomment-126970794
        if source == "" {