git commit -m "datasette --template-dir=mytemplates/" argument

You can now pass an additional argument specifying a directory to look for
custom templates in.

Datasette will fall back on the default templates if a template is not
found in that directory.

Refs #12, #153

datasette/app.py

@@ -771,7 +771,7 @@ class Datasette:
     def __init__(
             self, files, num_threads=3, cache_headers=True, page_size=100,
             max_returned_rows=1000, sql_time_limit_ms=1000, cors=False,
-            inspect_data=None, metadata=None, sqlite_extensions=None):
+            inspect_data=None, metadata=None, sqlite_extensions=None, template_dir=None):
         self.files = files
         self.num_threads = num_threads
         self.executor = futures.ThreadPoolExecutor(
@@ -786,6 +786,7 @@ class Datasette:
         self.metadata = metadata or {}
         self.sqlite_functions = []
         self.sqlite_extensions = sqlite_extensions or []
+        self.template_dir = template_dir
 
     def asset_urls(self, key):
         for url_or_dict in (self.metadata.get(key) or []):
@@ -892,10 +893,12 @@ class Datasette:
 
     def app(self):
         app = Sanic(__name__)
+        template_paths = []
+        if self.template_dir:
+            template_paths.append(self.template_dir)
+        template_paths.append(str(app_root / 'datasette' / 'templates'))
         self.jinja_env = Environment(
-            loader=FileSystemLoader([
+            loader=FileSystemLoader(template_paths),
-                str(app_root / 'datasette' / 'templates')
-            ]),
             autoescape=True,
         )
         self.jinja_env.filters['escape_css_string'] = escape_css_string

datasette/cli.py

@@ -156,7 +156,8 @@ def package(files, tag, metadata, extra_options, branch, **extra_metadata):
 )
 @click.option('--inspect-file', help='Path to JSON file created using "datasette build"')
 @click.option('-m', '--metadata', type=click.File(mode='r'), help='Path to JSON file containing license/source metadata')
-def serve(files, host, port, debug, reload, cors, page_size, max_returned_rows, sql_time_limit_ms, sqlite_extensions, inspect_file, metadata):
+@click.option('-t', '--template-dir', type=click.Path(exists=True, file_okay=False, dir_okay=True), help='Path to directory containing custom templates')
+def serve(files, host, port, debug, reload, cors, page_size, max_returned_rows, sql_time_limit_ms, sqlite_extensions, inspect_file, metadata, template_dir):
     """Serve up specified SQLite database files with a web UI"""
     if reload:
         import hupper
@@ -181,6 +182,7 @@ def serve(files, host, port, debug, reload, cors, page_size, max_returned_rows,
         inspect_data=inspect_data,
         metadata=metadata_data,
         sqlite_extensions=sqlite_extensions,
+        template_dir=template_dir,
     )
     # Force initial hashing/table counting
     ds.inspect()