Use minios disk package for cross-platform disk stats

[sanderpick]

Textile's powergate has a Lotus dependency. Powergate is leveraged by the hub, which has Linux and Darwin CLI builds. This syscall prevents us from releasing a Window build:

1 errors occurred:
--> windows/amd64 error: exit status 2
Stderr: # github.com/filecoin-project/sector-storage/stores
../../../go/pkg/mod/github.com/filecoin-project/sector-storage@v0.0.0-20200605192746-4b9317d1f08f/stores/interface.go:41:11: undefined: syscall.Statfs_t
../../../go/pkg/mod/github.com/filecoin-project/sector-storage@v0.0.0-20200605192746-4b9317d1f08f/stores/interface.go:42:12: undefined: syscall.Statfs

This PR just replaces syscall.Statfs with disk.GetInfo from https://github.com/minio/minio/tree/release/pkg/disk, which makes a library depending on Lotus compile on Windows.

[jsign]

Adding some extra info. Down the path of some dependency imports, the previous step to jump to this repo is the Lotus API using types for its API definitions: see here.

[magik6k]

Is there a way to import this without importing the whole minio dependency tree? (or a lighter library?)

[sanderpick]

Some other lighter packages that I found:

• go-disk-usage
• disk

Though, it's straightforward enough to just copy the minio implementation into here with the license. What's your preference?

[magik6k]

go-disk-usage looks good

[sanderpick]

Okay, migrated to go-disk-usage.

[sanderpick]

Note, this package doesn't handle the syscall error: https://github.com/ricochet2200/go-disk-usage/blob/master/du/diskusage.go#L16

[magik6k]

The same thing is now addressed in https://github.com/filecoin-project/sector-storage/pull/66/files#diff-3edd672f6d345b2738ba957c8bb19960R1

Thanks for the PR anyways

[magik6k]

Done in #66

[sanderpick]

Sure thing ;)