add tool to synchronize add-on repository with latest addonTemplate

.addonmergeignore

@@ -0,0 +1,2 @@
+# Files and directories ignored during template synchronization
+.addonmergeignore

docs/unitTesting.md

@@ -2,16 +2,47 @@
 
 This template provides a built-in unit testing structure powered by Python's standard `unittest` framework.
 
+Ensuring your add-on and tooling behavior remains consistent during development and following template updates is done through automated unit testing.
+
 ## Running Tests Locally
 
-To run the unit test suite locally using `uv`:
+For unit tests to execute successfully, target modules (such as `syncAddonWithTemplate.py`) must be located at the root of the repository as sibling files to the `tests/` directory (at the same hierarchical level). This ensures Python's module discovery properly imports scripts when `unittest` runs from the project root.
+
+### Run the Full Test Suite
+
+To run the entire unit test suite with automatic test discovery and detailed output for every executed test case:
 
 ``` bash
 uv run python -m unittest discover -s tests -v
 ```
 
-Or execute tests for a specific file:
+Here is what each part of the command does:
+* `uv run`: Executes the command within the virtual environment managed by `uv`.
+* `python -m unittest discover`: Automatically finds and runs all test files (matching `test*.py`) within the specified test directory.
+* `-s tests`: Sets the start directory for test discovery to the `tests/` folder.
+* `-v`: Enables verbose output, displaying the status and description of each test method individually.
 
-``` bash
-uv run python -m unittest -v tests/unit/template/test_sanity.py
-```
+### Run Specific Test Suites
+
+You can run individual test modules during development by specifying their path:
+
+* **Add-on Synchronization Tool Tests:**
+  ``` bash
+  uv run python -m unittest -v tests/unit/template/test_syncAddonWithTemplate.py
+  ```
+
+---
+
+## Synchronization Tool Test Suite Overview (`test_syncAddonWithTemplate.py`)
+
+The unit test suite covers key logic in `syncAddonWithTemplate.py`, ensuring AST-based config merges, file parsing, and formatting behave predictably across project updates:
+
+* **`testMergeLegacyBuildvarsWithOfficialTemplate`**: Validates the AST-based migration of legacy dictionary-based `buildVars.py` files into the official modern `AddonInfo` class structure.
+* **`testMergeModernBuildvarsMissingSpeechDictionaries`**: Ensures that missing modern attributes (like `speechDictionaries`) are injected into existing `buildVars.py` files without overwriting present configurations.
+* **`testSetupAddonMergeIgnore`**: Verifies that `.addonmergeignore` is automatically bootstrapped from the template if missing, preserved if already present, and left untouched during dry-run executions.
+* **`testAddonMergeIgnore`**: Confirms that files and patterns specified in `.addonmergeignore` are strictly excluded from being overwritten during full add-on synchronization.
+* **`testMergeBuildvarsAutoImportsOs`**: Confirms that `import os` is automatically prepended at the top of the merged `buildVars.py` file if any merged variable uses functions from the `os` module (e.g., `os.path.join`).
+* **`testFixTomlIndentation`**: Verifies that 4-space indentations are correctly converted into tabs inside `maintainers` or `authors` TOML array blocks while leaving other sections untouched.
+* **`testFormatAuthorList`**: Tests parsing of raw author strings (such as `"Name <email>"`) into `tomlkit` array objects with structured `name` and `email` key-value pairs, ensuring empty `email` fields are omitted for PEP 621 compliance.
+* **`testMergeDependencyLists`**: Checks that dependency lists are merged intelligently by base package name, updating outdated tool versions while preserving custom user dependencies.
+* **`testMergePyprojectTomlIntelligent`**: Verifies that `pyproject.toml` files are merged using `tomlkit` without creating duplicate dependencies or clobbering existing configuration sections.

pyproject.toml

@@ -29,10 +29,11 @@ Repository = "https://github.com/nvaccess/addonTemplate"
 # PEP 735 dependency groups. `uv sync` installs the `dev` group by default, which
 # pulls in every tool needed to build, translate, and lint the add-on.
 [dependency-groups]
-# Build add-on
+# Build add-on & repository synchronization machinery
 build = [
 	"scons==4.10.1",
 	"Markdown==3.10",
+	"tomlkit==0.15.0",
 ]
 # Translations management
 l10n = [
@@ -48,7 +49,7 @@ lint = [
 	"uv==0.11.15",
 	"ruff==0.14.5",
 	"prek==0.4.8",
-	"pyright[nodejs]==1.1.407",
+	"pyright[nodejs]==1.1.411",
 ]
 dev = [
 	{ include-group = "build" },
@@ -80,6 +81,7 @@ exclude = [
 	"__pycache__",
 	".venv",
 	"buildVars.py",
+	"syncAddonWithTemplate.py",
 	"tests",
 ]
 
@@ -119,6 +121,7 @@ exclude = [
 	".venv",
 	"site_scons",
 	".github/scripts",
+	"syncAddonWithTemplate.py",
 	"tests",
 	# When excluding concrete paths relative to a directory,
 	# not matching multiple folders by name e.g. `__pycache__`,
@@ -228,3 +231,6 @@ reportMissingTypeStubs = false
 
 # Bad rules
 # These are sorted alphabetically and should be enabled and moved to compliant rules section when resolved.
+
+[tool.setuptools]
+py-modules = []