fix: don't overwrite output pack by default

README.md

@@ -368,6 +368,7 @@ Options:
   -e, --external-files <path>  Emit external files.
   -p, --prefetch-urls <path>   Prefetch markdown links.
   -f, --flat                   Use the flat markdown format.
+  -o, --overwrite              Overwrite the output pack.
   -v, --version                Show the version and exit.
   -h, --help                   Show this message and exit.
 ```
@@ -389,6 +390,12 @@ $ lectern demo.md -r demo_resource_pack
 $ lectern demo.md -d demo_data_pack -r demo_resource_pack
 ```
 
+If you want to overwrite an existing data pack or resource pack you need to specify the `-o/--overwrite` option explicitly.
+
+```bash
+$ lectern demo.md --overwrite --data-pack demo_data_pack
+```
+
 You can also convert a combination of data packs and resource packs into a single markdown file.
 
 ```bash

lectern/cli.py

@@ -7,7 +7,7 @@
 from typing import Any, Optional, Tuple
 
 import click
-from beet import run_beet
+from beet import ErrorMessage, run_beet
 from beet.toolchain.cli import error_handler
 
 from lectern import __version__
@@ -53,6 +53,12 @@ def echo(*args: Any, **kwargs: Any):
     is_flag=True,
     help="Use the flat markdown format.",
 )
+@click.option(
+    "-o",
+    "--overwrite",
+    is_flag=True,
+    help="Overwrite the output pack.",
+)
 @click.version_option(
     __version__,
     "-v",
@@ -68,6 +74,7 @@ def lectern(
     external_files: Optional[str],
     prefetch_urls: Optional[str],
     flat: bool,
+    overwrite: bool,
 ):
     """Literate Minecraft data packs and resource packs."""
     config: Any
@@ -113,10 +120,13 @@ def lectern(
         }
 
     with run_beet(config) as beet_ctx:
-        if data_pack:
-            beet_ctx.data.save(path=data_pack, overwrite=True)
-        if resource_pack:
-            beet_ctx.assets.save(path=resource_pack, overwrite=True)
+        try:
+            if data_pack:
+                beet_ctx.data.save(path=data_pack, overwrite=overwrite)
+            if resource_pack:
+                beet_ctx.assets.save(path=resource_pack, overwrite=overwrite)
+        except FileExistsError as exc:
+            raise ErrorMessage(f"{exc} (run again with --overwrite)") from exc
 
 
 def main():