Update README.md

Author: dxa4481

README.md

@@ -26,20 +26,29 @@ pip install truffleHog
 
 ## Customizing
 
-Custom regexes can be added to the following file:
+Custom regexes can be added with the following flag `--rules /path/to/rules`. This should be a json file of the following format:
 ```
-truffleHog/truffleHog/regexChecks.py
+{
+    "RSA private key": "-----BEGIN EC PRIVATE KEY-----"
+}
 ```
 Things like subdomain enumeration, s3 bucket detection, and other useful regexes highly custom to the situation can be added.
 
 Feel free to also contribute high signal regexes upstream that you think will benifit the community. Things like Azure keys, Twilio keys, Google Compute keys, are welcome, provided a high signal regex can be constructed.
 
+Trufflehog's base rule set sources from https://github.com/dxa4481/truffleHogRegexes/blob/master/truffleHogRegexes/regexes.json
+
 ## How it works
 This module will go through the entire commit history of each branch, and check each diff from each commit, and check for secrets. This is both by regex and by entropy. For entropy checks, trufflehog will evaluate the shannon entropy for both the base64 char set and hexidecimal char set for every blob of text greater than 20 characters comprised of those character sets in each diff. If at any point a high entropy string >20 characters is detected, it will print to the screen.
 
 ## Help
 
 ```
+usage: trufflehog [-h] [--json] [--regex] [--rules RULES]
+                  [--entropy DO_ENTROPY] [--since_commit SINCE_COMMIT]
+                  [--max_depth MAX_DEPTH]
+                  git_url
+
 Find secrets hidden in the depths of git.
 
 positional arguments:
@@ -49,6 +58,7 @@ optional arguments:
   -h, --help            show this help message and exit
   --json                Output in JSON
   --regex               Enable high signal regex checks
+  --rules RULES         Ignore default regexes and source from json list file
   --entropy DO_ENTROPY  Enable entropy checks
   --since_commit SINCE_COMMIT
                         Only scan from a given commit hash