Document an universal ANSI Esc code regexp for models

- Updated the garderos model, as we have unit tests for it an it uses
ANSI ESC codes.
- This will help me to improve PR #3332 with an universal approach.
- No documentation to CHANGELOG.md, as documentation / change in
Garderos covered by unit tests

docs/Creating-Models.md

@@ -76,6 +76,29 @@ need to enable privileged mode, either without providing a password (by setting
 ```
 Note: remove `:telnet, ` if your device does not support telnet.
 
+### Common Task: remove ANSI escape codes
+> :warning: This common task is still experimental.
+> If it does not work for you, please open an issue so that we can adapt the
+> code snippet.
+
+Some devices produce ANSI escape codes to enhance the appearance of output.
+However, this can make prompt matching difficult and some of these ANSI escape
+codes might end up in the resulting configuration.
+
+You can remove most [ANSI escape codes](https://en.wikipedia.org/wiki/ANSI_escape_code#Control_Sequence_Introducer_commands) using the following Ruby
+code in your model:
+```
+  # Remove ANSI escape codes
+  expect /\e\[[0-?]*[ -\/]*[@-~]/ do |data, re|
+    data.gsub re, ''
+  end
+```
+Explanation of the Regular Expression:
+- `\e\[`  : Control Sequence Introducer (CSI), which starts with "ESC [".
+- `[0-?]*`: "parameter" bytes (range 0x30–0x3F, corresponding to ASCII `0–9:;<=>?`)
+- `[ -/]*`: "intermediate" bytes (range 0x20–0x2F, corresponding to ASCII ` !"#$%&'()*+,-./`)
+- `[@-~]` : the "final" byte (range 0x40–0x7E, corresponding to ASCII ``@A–Z[\]^_`a–z{|}~).[``)
+
 ## Extending an existing model with a new command
 
 The example below can be used to extend the `JunOS` model to collect the output of `show interfaces diagnostics optics` and append the output to the configuration file as a comment. This command retrieves DOM information on pluggable optics present in a `JunOS`-powered chassis.

lib/oxidized/model/garderos.rb

@@ -4,12 +4,12 @@ class Garderos < Oxidized::Model
   # Routers for harsh environments
   # grs = Garderos Router Software
 
-  # remove all ANSI escape codes, as GRS uses them :-(
-  # the prompt does not need to match escape codes, as they have been removed
-  expect /\e\[\d*m\r?/ do |data, re|
+  # remove ANSI escape codes
+  expect /\e\[[0-?]*[ -\/]*[@-~]/ do |data, re|
     data.gsub re, ''
   end
 
+  # the prompt does not need to match escape codes, as they have been removed above
   prompt /[\w-]+# /
   comment '# '