Version IDs for S3 and generations for GCS

docs/serving_files_from_google_cloud_storage.md

@@ -4,3 +4,9 @@ imgproxy can process images from Google Cloud Storage buckets. To use this featu
 
 1. Set `IMGPROXY_GCS_KEY` environment variable to the content of Google Cloud JSON key. Get more info about JSON keys: [https://cloud.google.com/iam/docs/creating-managing-service-account-keys](https://cloud.google.com/iam/docs/creating-managing-service-account-keys);
 2. Use `gs://%bucket_name/%file_key` as the source image URL.
+
+If you need to specify generation of the source object, you can use query string of the source URL:
+
+```
+gs://%bucket_name/%file_key?%generation
+```

docs/serving_files_from_s3.md

@@ -8,6 +8,12 @@ imgproxy can process images from S3 buckets. To use this feature, do the followi
 4. _(optional)_ Specify S3 endpoint with `IMGPROXY_S3_ENDPOINT`;
 5. Use `s3://%bucket_name/%file_key` as the source image URL.
 
+If you need to specify version of the source object, you can use query string of the source URL:
+
+```
+s3://%bucket_name/%file_key?%version_id
+```
+
 ### Setup credentials
 
 There are three ways to specify your AWS credentials. The credentials need to have read rights for all of the buckets given in the source URLs.

gcs_transport.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"log"
 	"net/http"
+	"strconv"
 	"strings"
 
 	"cloud.google.com/go/storage"
@@ -27,6 +28,11 @@ func newGCSTransport() http.RoundTripper {
 func (t gcsTransport) RoundTrip(req *http.Request) (resp *http.Response, err error) {
 	bkt := t.client.Bucket(req.URL.Host)
 	obj := bkt.Object(strings.TrimPrefix(req.URL.Path, "/"))
+
+	if g, err := strconv.ParseInt(req.URL.RawQuery, 10, 64); err == nil && g > 0 {
+		obj = obj.Generation(g)
+	}
+
 	reader, err := obj.NewReader(context.Background())
 
 	if err != nil {

s3transport.go

@@ -33,6 +33,11 @@ func (t s3Transport) RoundTrip(req *http.Request) (resp *http.Response, err erro
 		Bucket: aws.String(req.URL.Host),
 		Key:    aws.String(req.URL.Path),
 	}
+
+	if len(req.URL.RawQuery) > 0 {
+		input.VersionId = aws.String(req.URL.RawQuery)
+	}
+
 	s3req, _ := t.svc.GetObjectRequest(input)
 
 	s3err := s3req.Send()