Merge pull request #35 from github/elr/cmd-doc

add documentation for license extraction utility

cmd/doc.go

@@ -0,0 +1,21 @@
+/*
+Extracts license, deprecation, and exception ids from the official spdx license list data.
+The source data needs to be manually updated by copying the licenses.json file from
+https://github.com/spdx/license-list-data/blob/main/json/licenses.json and exceptions.json
+file from https://github.com/spdx/license-list-data/blob/main/json/exceptions.json.
+
+After running the extract command, the license_ids.json, deprecated_ids.json, and exception_ids.json
+files will be overwritten with the extracted ids.  These license ids can then be used to update the
+spdxexp/license.go file.
+
+Command to run all extractions (run command from the /cmd directory):
+
+	go run . extract -l -e
+
+Usage options:
+
+	-h: prints this help message
+	-l: Extract license ids
+	-e: Extract exception ids
+*/
+package main