Update README and inline docs on different remote caching providers

Author: adrienthebo

README.md

@@ -326,7 +326,11 @@ Using this mechanism you can also overwrite the default manifest entries, e.g. "
 Leeway is configured exclusively through the WORKSPACE.yaml/BUILD.yaml files and environment variables. The following environment
 variables have an effect on leeway:
 - `LEEWAY_WORKSPACE_ROOT`: Contains the path where to look for a WORKSPACE file. Can also be set using --workspace.
-- `LEEWAY_REMOTE_CACHE_BUCKET`: Enables remote caching using GCP buckets. Set this variable to the bucket name used for caching. When this variable is set, leeway expects "gsutil" in the path configured and authenticated so that it can work with the bucket.
+- `LEEWAY_REMOTE_CACHE_STORAGE`: Defines the remote caching storage provider. Valid values are "GCP" and "AWS". Defaults to "GCP".
+- `LEEWAY_REMOTE_CACHE_BUCKET`:  Enables remote caching using GCP or S3 buckets. Required credentials depend on the storage provider:
+    - `"GCP"`: leeway expects "gsutil" in the path configured and authenticated so that it can work with the bucket.
+    - `"AWS"`: leeway expects that AWS credentials have been provided and with read/write access to the S3 bucket.
+          For details on configuring AWS credentials see https://docs.aws.amazon.com/cli/latest/userguide/cli-configure-files.html
 - `LEEWAY_CACHE_DIR`: Location of the local build cache. The directory does not have to exist yet.
 - `LEEWAY_BUILD_DIR`: Working location of leeway (i.e. where the actual builds happen). This location will see heavy I/O which makes it advisable to place this on a fast SSD or in RAM.
 - `LEEWAY_YARN_MUTEX`: Configures the mutex flag leeway will pass to yarn. Defaults to "network". See https://yarnpkg.com/lang/en/docs/cli/#toc-concurrency-and-mutex for possible values.

cmd/root.go

@@ -80,9 +80,11 @@ var rootCmd = &cobra.Command{
 Leeway is configured exclusively through the WORKSPACE/BUILD files and environment variables. The following environment
 variables have an effect on leeway:
        <light_blue>LEEWAY_WORKSPACE_ROOT</>  Contains the path where to look for a WORKSPACE file. Can also be set using --workspace.
-  <light_blue>LEEWAY_REMOTE_CACHE_BUCKET</>  Enables remote caching using GCP buckets. Set this variable to the bucket name used for caching.
-                              When this variable is set, leeway expects "gsutil" in the path configured and authenticated so
-                              that it can work with the bucket.
+ <light_blue>LEEWAY_REMOTE_CACHE_STORAGE</>  Defines the remote caching storage provider. Valid values are "GCP" and "AWS". Defaults to "GCP".
+  <light_blue>LEEWAY_REMOTE_CACHE_BUCKET</>  Enables remote caching using GCP or S3 buckets. Required credentials depend on the storage provider:
+                             - GCP: leeway expects "gsutil" in the path configured and authenticated so that it can work with the bucket.
+                             - AWS: leeway expects that AWS credentials have been provided and with read/write access to the S3 bucket.
+                               For details on configuring AWS credentials see https://docs.aws.amazon.com/cli/latest/userguide/cli-configure-files.html
             <light_blue>LEEWAY_CACHE_DIR</>  Location of the local build cache. The directory does not have to exist yet.
             <light_blue>LEEWAY_BUILD_DIR</>  Working location of leeway (i.e. where the actual builds happen). This location will see heavy I/O
                               which makes it advisable to place this on a fast SSD or in RAM.