Change broadcast cmd to just take an argument instead of STDIN

Simpler

README.md

@@ -348,7 +348,7 @@ If you need separate env variables for different destinations, you can set them
 
 ### Using audit broadcasts
 
-If you'd like to broadcast audits of deploys, rollbacks, etc to a chatroom or elsewhere, you can configure the `audit_broadcast_cmd` setting with the path to a bin file that reads the audit line from STDIN, and then does whatever with it:
+If you'd like to broadcast audits of deploys, rollbacks, etc to a chatroom or elsewhere, you can configure the `audit_broadcast_cmd` setting with the path to a bin file that will be passed the audit line as the first argument:
 
 ```yaml
 audit_broadcast_cmd:
@@ -359,14 +359,13 @@ The broadcast command could look something like:
 
 ```bash
 #!/usr/bin/env bash
-read
-curl -q -d content="[My app] ${REPLY}" https://3.basecamp.com/XXXXX/integrations/XXXXX/buckets/XXXXX/chats/XXXXX/lines
+curl -q -d content="[My App] ${1}" https://3.basecamp.com/XXXXX/integrations/XXXXX/buckets/XXXXX/chats/XXXXX/lines
 ```
 
 That'll post a line like follows to a preconfigured chatbot in Basecamp:
 
 ```
-[My App] [2023-02-18 11:29:52] [dhh] Rolled back to version d264c4e92470ad1bd18590f04466787262f605de
+[My App] [dhh] Rolled back to version d264c4e92470ad1bd18590f04466787262f605de
 ```
 
 ### Using custom healthcheck path or port

lib/mrsk/commands/auditor.rb

@@ -11,9 +11,7 @@ class Mrsk::Commands::Auditor < Mrsk::Commands::Base
   # Runs locally
   def broadcast(line)
     if broadcast_cmd = config.audit_broadcast_cmd
-      pipe \
-        [ :echo, tagged_broadcast_line(line) ],
-        broadcast_cmd
+      [ broadcast_cmd, tagged_broadcast_line(line) ]
     end
   end
 

test/commands/auditor_test.rb

@@ -16,7 +16,7 @@ class CommandsAuditorTest < ActiveSupport::TestCase
 
   test "broadcast" do
     assert_match \
-      /echo '.* app removed container' \| bin\/audit_broadcast/,
+      /bin\/audit_broadcast '\[.*\] app removed container'/,
       new_command.broadcast("app removed container").join(" ")
   end