Add /config dir support

This commit adds support for a configuration directory (default `config`). The different pieces in this puzzle are:

* A new `--environment` (or `-e`) flag. This can also be set with the `HUGO_ENVIRONMENT` OS environment variable. The value for `environment` defaults to `production` when running `hugo` and `development` when running `hugo server`. You can set it to any value you want (e.g. `hugo server -e "Sensible Environment"`), but as it is used to load configuration from the file system, the letter case may be important. You can get this value in your templates with `{{ hugo.Environment }}`.
* A new `--configDir` flag (defaults to `config` below your project). This can also be set with `HUGO_CONFIGDIR` OS environment variable.

If the `configDir` exists, the configuration files will be read and merged on top of each other from left to right; the right-most value will win on duplicates.

Given the example tree below:

If `environment` is `production`, the left-most `config.toml` would be the one directly below the project (this can now be omitted if you want), and then `_default/config.toml` and finally `production/config.toml`. And since these will be merged, you can just provide the environment specific configuration setting in you production config, e.g. `enableGitInfo = true`. The order within the directories will be lexical (`config.toml` and then `params.toml`).

```bash
config
├── _default
│   ├── config.toml
│   ├── languages.toml
│   ├── menus
│   │   ├── menus.en.toml
│   │   └── menus.zh.toml
│   └── params.toml
├── development
│   └── params.toml
└── production
    ├── config.toml
    └── params.toml
```

Some configuration maps support the language code in the filename (e.g. `menus.en.toml`): `menus` (`menu` also works) and `params`.

Also note that the only folders with "a meaning" in the above listing is the top level directories below `config`. The `menus` sub folder is just added for better organization.

We use `TOML` in the example above, but Hugo also supports `JSON` and `YAML` as configuration formats. These can be mixed.

Fixes #5422

1 files changed, 6 insertions, 0 deletions

diff --git a/commands/commands_test.go b/commands/commands_test.go
index 84afe4419..9b9806694 100644
--- a/commands/commands_test.go
+++ b/commands/commands_test.go
@@ -56,8 +56,11 @@ func TestCommandsPersistentFlags(t *testing.T) {
 		check func(command []cmder)
 	}{{[]string{"server",
 		"--config=myconfig.toml",
+		"--configDir=myconfigdir",
 		"--contentDir=mycontent",
 		"--disableKinds=page,home",
+		"--environment=testing",
+		"--configDir=myconfigdir",
 		"--layoutDir=mylayouts",
 		"--theme=mytheme",
 		"--gc",
@@ -78,6 +81,7 @@ func TestCommandsPersistentFlags(t *testing.T) {
 			if b, ok := command.(commandsBuilderGetter); ok {
 				v := b.getCommandsBuilder().hugoBuilderCommon
 				assert.Equal("myconfig.toml", v.cfgFile)
+				assert.Equal("myconfigdir", v.cfgDir)
 				assert.Equal("mysource", v.source)
 				assert.Equal("https://example.com/b/", v.baseURL)
 			}
@@ -93,6 +97,7 @@ func TestCommandsPersistentFlags(t *testing.T) {
 		assert.True(sc.noHTTPCache)
 		assert.True(sc.renderToDisk)
 		assert.Equal(1366, sc.serverPort)
+		assert.Equal("testing", sc.environment)
 
 		cfg := viper.New()
 		sc.flagsToConfig(cfg)
@@ -233,6 +238,7 @@ Single: {{ .Title }}
 	writeFile(t, filepath.Join(d, "layouts", "_default", "list.html"), `
 
 List: {{ .Title }}
+Environment: {{ hugo.Environment }}
 
 `)