Allow to set cache dir in config file

commands/hugo.go

@@ -372,6 +372,11 @@ func InitializeConfig(subCmdVs ...*cobra.Command) error {
 		viper.Set("LayoutDir", layoutDir)
 	}
 
+	if cacheDir != "" {
+		viper.Set("CacheDir", cacheDir)
+	}
+
+	cacheDir = viper.GetString("cacheDir")
 	if cacheDir != "" {
 		if helpers.FilePathSeparator != cacheDir[len(cacheDir)-1:] {
 			cacheDir = cacheDir + helpers.FilePathSeparator

docs/content/extras/datadrivencontent.md

@@ -103,6 +103,8 @@ temporary directory.
 With the command-line flag `--cacheDir`, you can specify any folder on
 your system as a caching directory.
 
+You can also set `cacheDir` in the main configuration file.
+
 If you don't like caching at all, you can fully disable caching with the
 command line flag `--ignoreCache`.