* config: refactor ReadPath(s) methods without side-effects
Return the sources instead of modifying the state.
* config: clean data dir before every test
* config: add tests for config-file and config-dir
* config: add -config-format option
Starting with Consul 1.0 all config files must have a '.json' or '.hcl'
extension to make it unambigous how the data should be parsed. Some
automation tools generate temporary files by appending a random string
to the generated file which obfuscates the extension and prevents the
file type detection.
This patch adds a -config-format option which can be used to override
the auto-detection behavior by forcing all config files or all files
within a config directory independent of their extension to be
interpreted as of this format.
Fixes#3620
874e350b2f