Deployment improvements

Replace deploy.sh with deploy.py
Some updates to setup scripts, for more consistency
Split out some common unix setup tasks into a script that both mac and
linux scripts call.

deploy.py

@@ -0,0 +1,69 @@
+#!/usr/bin/env python3
+
+import sys
+from pathlib import Path
+
+home = Path.home().resolve().absolute()
+dotdir = Path(__file__).parent.resolve().absolute()
+
+simple = [
+    # 'gemrc',
+    'gitconfig',
+    'ideavimrc',
+    'lein',
+    # 'irbrc',
+    # 'nethackrc',
+    # 'spacemacs',
+    'tmux.conf',
+    'vimrc'
+]
+
+targeted = {
+    'doom': '.doom.d',
+    'fish': '.config/fish',
+}
+
+
+def deploy(source_name, target_name, dry_run=False):
+    source = dotdir.joinpath(source_name)
+    target = home.joinpath(target_name)
+    
+    if not source.exists():
+        raise FileNotFoundError(f"Asked to link {source_name}, which doesn't exist in {dotdir}.")
+
+    if target.exists():
+        if target.samefile(source):
+            print(f"{target}->{source} already linked.")
+            return
+        
+        backup_path = target.parent.joinpath(f"{target.name}.bak")
+
+        print(f"{target} moves to {backup_path}")
+        if not dry_run:
+            target.replace(backup_path)
+
+    if not target.parent.exists():
+        print(f"making parent directories of {target}")
+        if not dry_run:
+            target.parent.mkdir(parents=True)
+
+    print(f"linking {target} to {source}")
+    if not dry_run:
+        target.symlink_to(source)
+
+
+def main(dry_run=True):
+    for source in simple:
+        target = f".{source}" 
+        deploy(source, target, dry_run=dry_run)
+        
+    for source, target in targeted.items():
+        deploy(source, target, dry_run=dry_run)
+
+
+if __name__ == '__main__':
+    try:
+        main(False)
+    except FileNotFoundError as e:
+        print(e)
+        sys.exit(1)