Allow updating and replacing modules from mx.exe

content/en/docs/refguide/general/mx-command-line-tool/module.md

@@ -85,18 +85,46 @@ The `mx module-import` command imports a source module (*.mpk*) into an app.
 
 Use the following command pattern for `mx module-import`:
 
-`mx module-import MPK_PATH MPR_PATH` 
+`mx module-import MPK_PATH MPR_PATH [--import-mode <add|replace|update>] [--conflict <fail|take_mine|take_theirs>] [--metadata <take_new|take_existing|erase>]`
 
 For `MPK_PATH`, enter a *.mpk* file with the module you want to import.
 
 For `MPR_PATH`, enter a *.mpr* file of the project you want to import a module into.
 
+For `--import-mode`, enter one of the following values to control what happens when a module with the same name already exists in the app:
+
+* `add` – Add the module. Fails if a module with the same name already exists. This is the default.
+* `replace` – Replace the existing module. Fails with exit code 310 if no module with that name is found in the app.
+* `update` – Replace the module if it already exists, or add it if it does not.
+
+For `--conflict`, enter one of the following values to control what happens when a same-name module already exists. This applies to the `add` and `update` modes:
+
+* `fail` – Return an error. This is the default.
+* `take_mine` – Keep the existing module and skip the import silently.
+* `take_theirs` – Replace the existing module.
+
+For `--metadata`, enter one of the following values to control how marketplace identity fields are handled when a module is replaced. This option only takes effect when a replacement actually occurs:
+
+* `take_new` – Use the identity fields from the incoming module. This is the default.
+* `take_existing` – Copy the identity fields from the module being replaced.
+* `erase` – Clear all identity fields.
+
+Regardless of the chosen strategy, `FromAppStore` is always inherited from the existing module, and `AppStoreVersion`/`AppStoreVersionGuid` fall back to the existing values when the incoming module does not provide them.
+
 ### Examples
 
-Here is an example:
+Add a module to an app:
 
 `mx module-import MyNewModule.mpk MyApp.mpr`
 
+Replace an existing module, keeping its marketplace identity:
+
+`mx module-import MyNewModule.mpk MyApp.mpr --import-mode replace --metadata take_existing`
+
+Update a module if it exists or add it if not, overwriting on collision:
+
+`mx module-import MyNewModule.mpk MyApp.mpr --import-mode update --conflict take_theirs`
+
 ### Return Codes
 
 The command returns 0 if it is successful.
@@ -121,6 +149,9 @@ In case of errors, the exit code consists of three digits `XYZ`:
     * 6 – Project can't be loaded
     * 7 – Module can't be loaded
     * 8 – Import of a module failed. Resulting project can't be saved.
+    * 9 – File does not exist.
+    * 10 – `--import-mode replace` was specified but no module with that name exists in the project.
+    * 11 – The MPK file has an unrecognised extension.
 
 For example: