improve git secret usage output

src/commands/git_secret_usage.sh

@@ -22,4 +22,17 @@ function usage {
   local commands="add|cat|changes|clean|hide|init|killperson|list|remove|reveal|tell|usage|whoknows"
 
   echo "usage: git secret [$commands]"
+  echo "See 'git secret [command] -h' for information on each one"
+  echo " add [filename.txt] - adds file to be hidden. Also add this file to .gitignore"
+  echo " cat [filename.txt] - cats the decrypted contents of the named file to stdout"
+  echo " changes [filename.secret] - indicates if the file has changed since checkin"
+  echo " clean - deletes encrypted files"
+  echo " hide - encrypts (or re-encrypts) the files to be hidden"
+  echo " init - creates the .gitsecret directory and contents needed for git-secret"
+  echo " killperson [emails] - the reverse of 'tell', removes access for the named user"
+  echo " list - shows files to be hidden/encrypted, as in .gitsecret/paths/mapping.cfg"
+  echo " remove [files] - removes files from list of those to be hidden. Removes from mapping.cfg"
+  echo " reveal - decrypts all hidden files, as mentioned in mapping.cfg"
+  echo " tell [email] - add access for the user with imported public key with email"
+  echo " whoknows - shows list of email addresses associated with public keys that can reveal files"
 }