install: Skip templates and raw files that aren't out of date in the destination.

install.py

@@ -7,6 +7,7 @@ import socket
 import sys
 from functools import partial
 from pathlib import Path
+from typing import List
 
 import mako.lookup
 import mako.template
@@ -33,6 +34,17 @@ def get_base16(scheme, app, template='default'):
     return requests.get(base_url + output + '/base16-' + scheme + extension).text
 
 
+def is_outdated(src: List[Path], dst: Path) -> bool:
+    if not dst.exists():
+        return True
+
+    dst_modified = dst.stat().st_mtime
+    return any(
+        a_src.stat().st_mtime > dst_modified
+        for a_src in src
+    )
+
+
 def main():
     parser = argparse.ArgumentParser(
         description='Generates and installs dotfiles for this host.',
@@ -56,6 +68,11 @@ def main():
         type=Path,
         default=os.environ.get('HOME') or Path.home(),
     )
+    parser.add_argument(
+        '-f', '--force',
+        help='Force overwrite all files even if they are not considered outdated.',
+        action='store_true'
+    )
     args = parser.parse_args()
 
     raw_dir = args.dotfiles / 'raw'
@@ -82,6 +99,8 @@ def main():
             continue
         rel_path = raw_path.relative_to(raw_dir)
         output_path = args.home / rel_path
+
+        if args.force or is_outdated([raw_path], output_path):
             print(rel_path)
             output_path.parent.mkdir(parents=True, exist_ok=True)
             shutil.copy(raw_path, output_path)
@@ -90,6 +109,9 @@ def main():
         if not template_path.is_file():
             continue
         rel_path = template_path.relative_to(templates_dir)
+        output_path = args.home / template_path.relative_to(templates_dir)
+
+        if args.force or is_outdated([template_path, host_filename], output_path):
             print(rel_path)
             template = mako.template.Template(
                 filename=str(template_path),
@@ -100,7 +122,6 @@ def main():
                 host=host_config,
                 get_base16=partial(get_base16, host_config.get('base16-scheme', 'default-dark')),
             )
-        output_path = args.home / template_path.relative_to(templates_dir)
             output_path.parent.mkdir(parents=True, exist_ok=True)
             with open(output_path, 'w+') as output_file:
                 output_file.write(output)