Allow specifying config via SNCLIRC environment variable

[vrillusions]

Will now check the following places for a config file and will try the first one in list:

• value specified with --config
• value from SNCLI environment variable if set
• ~/.snclirc

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I try to make use of the ~/.config directory for storing config files. This was the smallest change I could figure out to achieve this. This lets me set export SNCLI="${HOME}/.config/sncli/snclirc" where I can then specify directories for any other config item (ex changing the path of the db directory)

Some basic testing to verify logic:

$ pipenv run ./sncli
Config file not found: '/home/vr/.snclirc'.
$ pipenv run ./sncli --config /tmp/nonexistent-file
Config file not found: '/tmp/nonexistent-file'.
$ SNCLIRC=/tmp/nonexistent-file-from-env pipenv run ./sncli --config /tmp/nonexistent-file
Config file not found: '/tmp/nonexistent-file'.
$ SNCLIRC=/tmp/nonexistent-file-from-env pipenv run ./sncli
Config file not found: '/tmp/nonexistent-file-from-env'.

[vrillusions]

Updated the section in README. Couldn't think of a good way to update the usage output to mention the environment variable. In a lot of other projects it seems like environment variables is an advanced option and usually just mentioned in README or other online documentation.

[samuelallan72]

Thanks!