Added a scenario to the help messages (#2121)

Author: gapra-msft

cmd/helpMessages.go

@@ -130,6 +130,10 @@ Download all the versions of a blob from Azure Storage to local directory. Ensur
 
   - azcopy cp "https://[srcaccount].blob.core.windows.net/[containername]/[blobname]" "/path/to/dir" --list-of-versions="/another/path/to/dir/[versionidsFile]"
 
+Copy a subset of files within a flat container by using a wildcard symbol (*) in the container name without listing all files in the container.
+
+  - azcopy cp "https://[srcaccount].blob.core.windows.net/[containername]/*" "/path/to/dir" --include-pattern="1*"
+
 Copy a single blob to another blob by using a SAS token.
 
   - azcopy cp "https://[srcaccount].blob.core.windows.net/[container]/[path/to/blob]?[SAS]" "https://[destaccount].blob.core.windows.net/[container]/[path/to/blob]?[SAS]"