docs: improve Singularity image source docs (#1190)

README.md

@@ -23,7 +23,7 @@ For commercial support options with Syft or Grype, please [contact Anchore](http
 
 ## Features
 - Generates SBOMs for container images, filesystems, archives, and more to discover packages and libraries
-- Supports OCI and Docker image formats
+- Supports OCI, Docker and [Singularity](https://github.com/sylabs/singularity) image formats
 - Linux distribution identification
 - Works seamlessly with [Grype](https://github.com/anchore/grype) (a fast, modern vulnerability scanner)
 - Able to create signed SBOM attestations using the [in-toto specification](https://github.com/in-toto/attestation/blob/main/spec/README.md)
@@ -119,6 +119,9 @@ Syft can generate a SBOM from a variety of sources:
 # catalog a container image archive (from the result of `docker image save ...`, `podman save ...`, or `skopeo copy` commands)
 syft path/to/image.tar
 
+# catalog a Singularity Image Format (SIF) container
+syft path/to/image.sif
+
 # catalog a directory
 syft path/to/dir
 ```

cmd/syft/cli/packages.go

@@ -25,12 +25,12 @@ const (
 
   Supports the following image sources:
     {{.appName}} {{.command}} yourrepo/yourimage:tag     defaults to using images from a Docker daemon. If Docker is not present, the image is pulled directly from the registry.
-    {{.appName}} {{.command}} path/to/a/file/or/dir      a Docker tar, OCI tar, OCI directory, or generic filesystem directory
+    {{.appName}} {{.command}} path/to/a/file/or/dir      a Docker tar, OCI tar, OCI directory, SIF container, or generic filesystem directory
 `
 
 	schemeHelpHeader = "You can also explicitly specify the scheme to use:"
 	imageSchemeHelp  = `    {{.appName}} {{.command}} docker:yourrepo/yourimage:tag            explicitly use the Docker daemon
-    {{.appName}} {{.command}} podman:yourrepo/yourimage:tag        	   explicitly use the Podman daemon
+    {{.appName}} {{.command}} podman:yourrepo/yourimage:tag            explicitly use the Podman daemon
     {{.appName}} {{.command}} registry:yourrepo/yourimage:tag          pull image directly from a registry (no container runtime required)
     {{.appName}} {{.command}} docker-archive:path/to/yourimage.tar     use a tarball from disk for archives created from "docker save"
     {{.appName}} {{.command}} oci-archive:path/to/yourimage.tar        use a tarball from disk for OCI archives (from Skopeo or otherwise)