[mdbook Plugin] Add gitinfo to sidebar

mdBook_plugin_gitinfo.py

## Usage:
## 
## 1. Add this script next to `book.toml` under file name `mdbook_plugin_gitinfo.py`
## 2. Update `book.toml`:
## 
##     ```toml
##     [preprocessor.gitinfo]
##     command = "python3 mdbook_plugin_gitinfo.py"
##     renderers = ["html"]
##     ```

import json
import subprocess
import sys
from typing import Any, Dict, List, Optional, TypedDict, Union


class Book(TypedDict):
    context: "BookContext"
    content: "BookContent"


class BookContext(TypedDict):
    root: str
    config: Dict[str, Any]
    renderer: str
    mdbook_version: str


class BookContent(TypedDict):
    sections: List[Union[Dict[str, Any], str]]


def read_book() -> Book:
    context, content = json.load(sys.stdin)
    return {"context": context, "content": content}


def write_book(book: Book) -> None:
    json.dump(book["content"], sys.stdout)


def plugin_add_version(book: Book) -> Book:
    gitinfo = get_gitinfo()
    version = "ERR: No Git Information" if gitinfo is None else gitinfo
    book["content"]["sections"].append("Separator")
    book["content"]["sections"].append(
        {
            "Chapter": {
                "name": f"Version: {version}",
                "content": "",
                "sub_items": [],
                "parent_names": [],
            }
        }
    )
    return book


def get_gitinfo() -> Optional[str]:
    result = subprocess.run(["git", "describe", "--always"], capture_output=True)
    return result.stdout.decode("utf-8") if result.returncode == 0 else None


def main():
    book = read_book()
    book = plugin_add_version(book)
    write_book(book)


if __name__ == "__main__":
    ## Did we receive an argument?
    if len(sys.argv) > 1:
        ## Is the call a "support" predicate?
        if sys.argv[1] == "supports":
            ## We support all kind of renderers:
            sys.exit(0)

    ## Run the plugin:
    main()