Add support for automatically symlinking

run.py

@@ -9,10 +9,21 @@ out_directory = './out/'
 # Applied in order, later files override earlier files
 env_files = ['./vars.env', './local.env']
 
+import argparse
+import difflib
 import jinja2
+import sys
 import re
 import os
 
+parser = argparse.ArgumentParser(description='Fill out configuration templates.')
+parser.add_argument('-f', '--force', default=False, action=argparse.BooleanOptionalAction, help='Force overwriting of existing files in output')
+parser.add_argument('-l', '--link', default=False, action=argparse.BooleanOptionalAction, help='Automatically create symlinks (based on the symlink comment in the templates, must be on first line of template)')
+parser.add_argument('-d', '--diff', default=False, action=argparse.BooleanOptionalAction, help='Show the diff of configuration files if file already exists')
+parser.add_argument('--dryrun', default=False, action=argparse.BooleanOptionalAction, help='Do not modify any files.')
+args = parser.parse_args()
+del parser
+
 def main():
     key_value_store = create_key_value_store()
     template_files = find_all_templates()
@@ -77,8 +88,50 @@ def convert_template(env, template, key_value_store, out):
     if not os.path.isdir(out_dir_name):
         os.makedirs(out_dir_name)
 
-    with open(out, 'w') as file:
-        file.write(rendered)
+    if os.path.isfile(out) and not args.force:
+        if args.diff:
+            with open(out) as file:
+                current = file.read()
+
+            for line in difflib.unified_diff(current.split('\n'), rendered.split('\n'), fromfile=out, tofile=out+'.new', lineterm=''):
+                print(line, file=sys.stderr)
+
+        if not args.force:
+            print(f"File `{out}` already exists, will not overwrite. Rerun with `-f` to force overwriting existing files.", file=sys.stderr)
+            return
+
+    if not args.dryrun:
+        with open(out, 'w') as file:
+            file.write(rendered)
+    else:
+        print(f'Would write rendered template to `{out}`.')
+
+    if args.link:
+        first_line = source.split('\n')[0]
+        m = re.search(r'symlink\{([^}]+)\}', first_line)
+
+        if m is None:
+            return
+
+        symlink_location = os.path.expanduser(m.group(1))
+
+        create_symlink(out, symlink_location)
+
+def create_symlink(source, destination):
+    if os.path.exists(destination):
+        if not args.force:
+            print('`{destination}` already exists, will not overwrite. Rerun with `-f` to force overwiring existing files.', file=sys.stderr)
+            return
+
+        if not args.dryrun:
+            os.remove(destination)
+        else:
+            print(f'Would remove `{destination}`.')
+
+    if not args.dryrun:
+        os.symlink(source, destination)
+    else:
+        print(f'Would create symlink `{destination}`->`{source}`.')
 
 if __name__ == '__main__':
     main()