Add base-path option to the codechin cli arguments

[HoOngEe]

Now It's possible to specify base-path on which the keys and db directory will be created when running codechain. But there already are options db-path and keys-path.
The rule relating to db-path, keys-path and base-path is like following:

db-path and keys-path have higher priority than base-path so if
both db-path and keys-path are set, base-path becomes meaningless.

it closes #236

[sgkim126]

You don't need this change.

[HoOngEe]

Without this change, the code in the line https://github.com/CodeChain-io/codechain/pull/1499/files/3c283f526dfb43ca1261fa5a77f090e2626b41c7#diff-22a0b3dcef5d27fab89655ebdb330967R257 could be a cause of panic.
Do I need to remove this change and use unwrap_or for the line mentioned above?

[sgkim126]

Why does it panic when you remove an empty line?

[HoOngEe]

Oh I'm sorry I misunderstood that you mentioned about the +base_path = "." change.

[sgkim126]

Hi @majecty @foriequal0,

I have a question about the behavior of a relative path.
What do you expect when you specify base-dir and specify db-path as a relative path?
A relative path from the current working directory? or from the base dir?

[majecty]

I'm not familiar with the setting two paths in CLI.
I found that in the Parity's config, the DB path is relative to the base path.
https://github.com/paritytech/parity-ethereum/blob/7c335e87642b848f61ab3ee7bbff5964b53d6f11/util/dir/src/lib.rs#L179

[sgkim126]

I think it's better to merge it for now and implement a sandbox correctly in the future.
Let's merge it.