Update readme

Author: 1e100

BUILD.main

@@ -3,5 +3,5 @@ load("@rules_cc//cc:defs.bzl", "cc_binary")
 cc_binary(
     name = "hello_minio",
     srcs = ["main.cc"],
-    data = ["@archive_minio//:files"],
+    data = ["@archive_gcloud//:files"],
 )

README.md

@@ -1,13 +1,20 @@
 # Cloud archive
 
-This `WORKSPACE` rule for Google Bazel lets you securely download private
-workspace dependencies from S3 or Minio.
+This set of `WORKSPACE` rules for Bazel lets you securely download private
+workspace dependencies from Google Cloud Storage, S3, Minio, or Backblaze B2.
+This can be useful when pulling data, code, and binary dependencies from these
+storage backends into your Bazel build.
 
 ## Requirements
 
 This currently only works on Linux, although adapting it to macOS and Windows
 shouldn't be difficult.
 
+### Google Cloud storage
+
+The `gsutil` command must be installed, and authenticated using `gcloud auth
+login`.
+
 ### S3
 
 AWS CLI is required to be in the path for S3 support, and must be set
@@ -20,11 +27,23 @@ multiple profiles.
 Likewise for Minio, `mc` command should be in the path, and Minio should be set
 up such that `mc cp` is able to download the referenced files.
 
+### Backblaze
+
+The `b2` command line utility must be installed and configured to access the
+account as per [the
+instructions](https://www.backblaze.com/b2/docs/quick_command_line.html).
+
 ## Usage
 
 Please refer to `WORKSPACE` file in this repository for an example of how to
 use this.
 
+## How to test
+
+To test, you will need to point the workspace targets to your own cloud
+storage, as well as initialize cloud storage on your machine to the point where
+the typical `cp` command works.
+
 ## Future work
 
 Quite obviously this can also be adapted to other cloud storage providers,

WORKSPACE

@@ -1,6 +1,6 @@
 workspace(name = "cloud_archive")
 
-load(":cloud_archive.bzl", "minio_archive", "s3_archive")
+load(":cloud_archive.bzl", "minio_archive", "s3_archive", "gs_archive")
 
 s3_archive(
     name = "archive_s3",
@@ -18,3 +18,12 @@ minio_archive(
     sha256 = "bf4dd5304180561a745e816ee6a8db974a3fcf5b9d706a493776d77202c48bc9",
     strip_prefix = "cloud_archive_test",
 )
+
+gs_archive(
+    name = "archive_gcloud",
+    build_file = "//:BUILD.archive",
+    bucket = "depthwise-temp",
+    file_path = "cloud_archive_test.tar.gz",
+    sha256 = "bf4dd5304180561a745e816ee6a8db974a3fcf5b9d706a493776d77202c48bc9",
+    strip_prefix = "cloud_archive_test",
+)

main.cc

@@ -4,7 +4,7 @@ int main() {
   printf("File contents:\n");
   size_t bytes_read = 0;
   char buf[256];
-  FILE* f = fopen("external/archive_minio/cloud_archive_test.txt", "r");
+  FILE* f = fopen("external/archive_gcloud/cloud_archive_test.txt", "r");
   if (f == nullptr) {
     fprintf(stderr, "Failed to open file.");
     return 1;