* It seems common enough that flags may be defined from PFlags be
retrieved as a sub Viper similar to getting it from Yaml or other
configuration structures. This allows flags to be bound one-to-one
with how a config file may be structured.
* This is partially based on #331 for the find boolean flag
* fixes#368
* When passing nil to BindPFlag or BindPFlags, the value is set to
a struct and passed as an interface. That struct never checks for the
flag(set) being nil. Thus, it makes sense to check before it's set to
the struct.
* fixes#422
- Don't expand user home directory for variable names that simply have a
HOME prefix;
- Support expansion of variables not followed by the path separator.
* add parsing for stringToString flags
* add logic to return flags default if not val set, add a test
* extract parsing into single func
* add a few more cases
* return nil if unable to parse instead of panicing
* return map[string]interface in order to work with cast.ToStringMap
* mostly copy pflags implementation of the conversion to a stringtostring
* Add support to save file with no extension
The support introduced for files with no file extension is only partial as trying to save the config file would fail with `<file name> requires valid extension`
This adds support to saving such files
* Only consider files without extension if the config type is explicitly specified
* Hides unused variable in test
* First check for config type then for file without extension
