docs: update CLI reference documentation and prompt data

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Author: github-actions[bot]

docs/cli-reference/base-options.md

@@ -5,6 +5,7 @@
 | Option | Description |
 |--------|-------------|
 | [`--encoding`](#encoding) | Specify character encoding for input and output files. |
+| [`--external-ref-mapping`](#external-ref-mapping) | Map external `$ref` files to Python packages. |
 | [`--input`](#input) | Specify the input schema file path. |
 | [`--input-file-type`](#input-file-type) | Specify the input file type for code generation. |
 | [`--input-model`](#input-model) | Import a Python type or dict schema from a module. |
@@ -74,6 +75,83 @@ Default is UTF-8, which is the standard encoding for JSON and most modern text f
 
 ---
 
+## `--external-ref-mapping` {#external-ref-mapping}
+
+Map external `$ref` files to Python packages.
+
+Use `--external-ref-mapping FILE_PATH=PYTHON_PACKAGE` to import referenced models from an existing package,
+instead of generating duplicate classes from external schema files.
+
+!!! tip "Usage"
+
+    ```bash
+    datamodel-codegen --input schema.json --input-file-type openapi --external-ref-mapping common.yaml=mypackage.shared.models # (1)!
+    ```
+
+    1. :material-arrow-left: `--external-ref-mapping` - the option documented here
+
+??? example "Examples"
+
+    **Input Schema:**
+
+    ```yaml
+    openapi: "3.0.3"
+    info:
+      title: API
+      version: "1.0.0"
+    paths: {}
+    components:
+      schemas:
+        UserResponse:
+          type: object
+          properties:
+            user:
+              $ref: "common.yaml#/components/schemas/User"
+            request_id:
+              type: string
+          required:
+            - user
+            - request_id
+        ErrorResponse:
+          type: object
+          properties:
+            error:
+              $ref: "common.yaml#/components/schemas/Error"
+            timestamp:
+              type: string
+              format: date-time
+          required:
+            - error
+            - timestamp
+    ```
+
+    **Output:**
+
+    ```python
+    # generated by datamodel-codegen:
+    #   filename:  api.yaml
+    #   timestamp: 2019-07-26T00:00:00+00:00
+    
+    from __future__ import annotations
+    
+    from datetime import datetime
+    
+    from mypackage.shared.models import Error, User
+    from pydantic import BaseModel
+    
+    
+    class UserResponse(BaseModel):
+        user: User
+        request_id: str
+    
+    
+    class ErrorResponse(BaseModel):
+        error: Error
+        timestamp: datetime
+    ```
+
+---
+
 ## `--input` {#input}
 
 Specify the input schema file path.

docs/cli-reference/index.md

@@ -8,7 +8,7 @@ This documentation is auto-generated from test cases.
 
 | Category | Options | Description |
 |----------|---------|-------------|
-| 📁 [Base Options](base-options.md) | 9 | Input/output configuration |
+| 📁 [Base Options](base-options.md) | 10 | Input/output configuration |
 | 🔧 [Typing Customization](typing-customization.md) | 29 | Type annotation and import behavior |
 | 🏷️ [Field Customization](field-customization.md) | 24 | Field naming and docstring behavior |
 | 🏗️ [Model Customization](model-customization.md) | 39 | Model generation behavior |
@@ -77,6 +77,7 @@ This documentation is auto-generated from test cases.
 - [`--encoding`](base-options.md#encoding)
 - [`--enum-field-as-literal`](typing-customization.md#enum-field-as-literal)
 - [`--enum-field-as-literal-map`](typing-customization.md#enum-field-as-literal-map)
+- [`--external-ref-mapping`](base-options.md#external-ref-mapping)
 - [`--extra-fields`](field-customization.md#extra-fields)
 - [`--extra-template-data`](template-customization.md#extra-template-data)
 

docs/cli-reference/quick-reference.md

@@ -17,6 +17,7 @@ datamodel-codegen [OPTIONS]
 | Option | Description |
 |--------|-------------|
 | [`--encoding`](base-options.md#encoding) | Specify character encoding for input and output files. |
+| [`--external-ref-mapping`](base-options.md#external-ref-mapping) | Map external `$ref` files to Python packages. |
 | [`--input`](base-options.md#input) | Specify the input schema file path. |
 | [`--input-file-type`](base-options.md#input-file-type) | Specify the input file type for code generation. |
 | [`--input-model`](base-options.md#input-model) | Import a Python type or dict schema from a module. |
@@ -252,6 +253,7 @@ All options sorted alphabetically:
 - [`--encoding`](base-options.md#encoding) - Specify character encoding for input and output files.
 - [`--enum-field-as-literal`](typing-customization.md#enum-field-as-literal) - Convert all enum fields to Literal types instead of Enum cla...
 - [`--enum-field-as-literal-map`](typing-customization.md#enum-field-as-literal-map) - Override enum/literal generation per-field via JSON mapping.
+- [`--external-ref-mapping`](base-options.md#external-ref-mapping) - Map external `$ref` files to Python packages.
 - [`--extra-fields`](field-customization.md#extra-fields) - Configure how generated models handle extra fields not defin...
 - [`--extra-template-data`](template-customization.md#extra-template-data) - Pass custom template variables from JSON file for code gener...
 - [`--field-constraints`](field-customization.md#field-constraints) - Generate Field() with validation constraints from schema.

src/datamodel_code_generator/prompt_data.py

@@ -46,6 +46,7 @@
     "--encoding": "Specify character encoding for input and output files.",
     "--enum-field-as-literal": "Convert all enum fields to Literal types instead of Enum classes.",
     "--enum-field-as-literal-map": "Override enum/literal generation per-field via JSON mapping.",
+    "--external-ref-mapping": "Map external `$ref` files to Python packages.",
     "--extra-fields": "Configure how generated models handle extra fields not defined in schema.",
     "--extra-template-data": "Pass custom template variables from JSON file for code generation.",
     "--field-constraints": "Generate Field() with validation constraints from schema.",