UG fix

docs/UserGuide.md

@@ -241,6 +241,7 @@ Furthermore, certain edits can cause the AddressBook to behave in unexpected way
 Team size: 4
 
 1. Improve readability of command history list: As of v1.3, the output of each command in the history is verbose, and introduces a lot of user-unfriendly code to the user. We plan to show only the command output that was typed by the user.
+2. Comprehensiveness of error messages: Error messages for list indexes <= 0 are inconsistent with positive indexes, even though the index is compliant with the command format. Examples of commands requiring indexes are `delete`, `edit`, `history`. We plan to ensure consistency with the error message so long as it is an index value.
 
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src/main/java/seedu/address/logic/commands/HistoryCommand.java

@@ -19,9 +19,9 @@ public class HistoryCommand extends Command {
     public static final String COMMAND_WORD = "history";
 
     public static final String MESSAGE_USAGE = COMMAND_WORD
-            + ": Lists command history. Runs the command when index is specified. \n"
+            + ": Lists command history. Runs the command when INDEX is specified. \n"
             + "Parameters: INDEX (must be a positive integer)\n"
-            + "Example: " + COMMAND_WORD + " 1";
+            + "Example: " + COMMAND_WORD + ", " + COMMAND_WORD + " 1";
 
     public static final String MESSAGE_HISTORY_SUCCESS = "Command History listed.";