go-ipfs-config: S3 datastore support

To test it, set up an S3 bucket (in an AWS region that is not US
Standard, for read-after-write consistency), run `ipfs init`, then
edit `~/.ipfs/config` to say

      "Datastore": {
        "Type": "s3",
        "Region": "us-west-1",
        "Bucket": "mahbukkit",
        "ACL": "private"
      },

with the right values. Set `AWS_ACCESS_KEY_ID` and
`AWS_SECRET_ACCESS_KEY` in the environment and you should be able to
run `ipfs add` and `ipfs cat` and see the bucket be populated.

No automated tests exist, unfortunately. S3 is thorny to simulate.

License: MIT
Signed-off-by: Tommi Virtanen <tv@eagain.net>

config/datastore.go

@@ -1,5 +1,9 @@
 package config
 
+import (
+	"encoding/json"
+)
+
 // DefaultDataStoreDirectory is the directory to store all the local IPFS data.
 const DefaultDataStoreDirectory = "datastore"
 
@@ -10,6 +14,22 @@ type Datastore struct {
 	StorageMax         string // in B, kB, kiB, MB, ...
 	StorageGCWatermark int64  // in percentage to multiply on StorageMax
 	GCPeriod           string // in ns, us, ms, s, m, h
+
+	Params *json.RawMessage
+}
+
+func (d *Datastore) ParamData() []byte {
+	if d.Params == nil {
+		return nil
+	}
+
+	return []byte(*d.Params)
+}
+
+type S3Datastore struct {
+	Region string `json:"region"`
+	Bucket string `json:"bucket"`
+	ACL    string `json:"acl"`
 }
 
 // DataStorePath returns the default data store path given a configuration root