feat: add support for pre-update and post-update messages (#1288)

* feat: add support for pre-update and post-update messages

* test: use verbose regex syntax

Author: sisp

copier/main.py

@@ -805,12 +805,14 @@ def run_update(self) -> None:
             # review the diff before committing; so we can safely avoid
             # asking for confirmation
             raise UserMessageError("Enable overwrite to update a subproject.")
+        self._print_message(self.template.message_before_update)
         if not self.quiet:
             # TODO Unify printing tools
             print(
                 f"Updating to template version {self.template.version}", file=sys.stderr
             )
         self._apply_update()
+        self._print_message(self.template.message_after_update)
 
     def _apply_update(self):
         subproject_top = Path(

copier/template.py

@@ -309,11 +309,21 @@ def message_after_copy(self) -> str:
         """Get message to print after copy action specified in the template."""
         return self.config_data.get("message_after_copy", "")
 
+    @cached_property
+    def message_after_update(self) -> str:
+        """Get message to print after update action specified in the template."""
+        return self.config_data.get("message_after_update", "")
+
     @cached_property
     def message_before_copy(self) -> str:
         """Get message to print before copy action specified in the template."""
         return self.config_data.get("message_before_copy", "")
 
+    @cached_property
+    def message_before_update(self) -> str:
+        """Get message to print before update action specified in the template."""
+        return self.config_data.get("message_before_update", "")
+
     @cached_property
     def metadata(self) -> AnyByStrDict:
         """Get template metadata.

docs/configuring.md

@@ -1028,6 +1028,28 @@ The message is suppressed when Copier is run in [quiet mode][quiet].
         2. Read "CONTRIBUING.md" and start coding.
     ```
 
+### `message_after_update`
+
+-   Format: `str`
+-   CLI flags: N/A
+-   Default value: `""`
+
+Like [`message_after_copy`][message_after_copy] but printed after
+[_updating_](updating.md) a project.
+
+!!! example
+
+    ```yaml title="copier.yml"
+    project_name:
+        type: str
+        help: An awesome project needs an awesome name. Tell me yours.
+
+    _message_after_update: |
+        Your project "{{ project_name }}" has been updated successfully!
+        In case there are any conflicts, please resolve them. Then,
+        you're done.
+    ```
+
 ### `message_before_copy`
 
 -   Format: `str`
@@ -1051,6 +1073,29 @@ Like [`message_after_copy`][message_after_copy] but printed _before_
         generate a tailored project for you.
     ```
 
+### `message_before_update`
+
+-   Format: `str`
+-   CLI flags: N/A
+-   Default value: `""`
+
+Like [`message_before_copy`][message_after_copy] but printed before
+[_updating_](updating.md) a project.
+
+!!! example
+
+    ```yaml title="copier.yml"
+    project_name:
+        type: str
+        help: An awesome project needs an awesome name. Tell me yours.
+
+    _message_before_update: |
+        Thanks for updating your project using our template.
+
+        You'll be asked a series of questions whose answers are pre-populated
+        with previously entered values. Feel free to change them as needed.
+    ```
+
 ### `migrations`
 
 -   Format: `List[dict]`