boxboat
Double quote YAML strings
config-merge uses YAML.stringify() to format the merged output as YAML.
While YAML.stringify() outputs YAML version 1.2 by default (https://eemeli.org/yaml/#document-options), the merged output may be consumed/parsed by other applications that expect YAML version 1.1. This is normally not an issue, except when it comes to yes/no strings. By default, YAML.stringify() formats strings unquoted. YAML version 1.2 parses unquoted yes/no strings as strings, while YAML version 1.1 parses unquoted yes/no strings as true/false booleans (https://eemeli.org/yaml/#version-differences).
An easy solution is to configure YAML.stringify() to double-quote all strings by default, by setting defaultStringType to QUOTE_DOUBLE (https://eemeli.org/yaml/#tostring-options). This will have no impact on YAML version 1.2 parsers, but fixes the issue with YAML version 1.1 parsers when it comes to yes/no strings.
