feat(setup): add -f/--filter to install a subset of profile paths

setup.py

@@ -206,6 +206,26 @@ class Resolved:
     system_installs: list[str]
 
 
+def apply_filter(ctx: Context, resolved: Resolved, filters: list[str]) -> Resolved:
+    wanted = set(filters)
+    symlinks = [p for p in resolved.symlinks if p in wanted]
+    symlink_map = {s: d for s, d in resolved.symlink_map.items() if s in wanted}
+    copies = [p for p in resolved.copies if p in wanted]
+    system_installs = [p for p in resolved.system_installs if p in wanted]
+
+    matched = set(symlinks) | set(symlink_map) | set(copies) | set(system_installs)
+    for f in wanted - matched:
+        ctx.error(f"--filter path not in selected profiles: {f!r}")
+
+    return Resolved(
+        pkgs=[],
+        symlinks=symlinks,
+        symlink_map=symlink_map,
+        copies=copies,
+        system_installs=system_installs,
+    )
+
+
 def resolve_profiles(ctx: Context, profile_names: list[str]) -> Resolved:
     pkgs: list[Pkg] = []
     symlinks: list[str] = []
@@ -461,7 +481,7 @@ def parse_args() -> argparse.Namespace:
         description="Install dotfiles and system configuration.",
     )
     parser.add_argument(
-        "-f",
+        "-F",
         "--force",
         action="store_true",
         help="Overwrite any existing links or files",
@@ -491,6 +511,19 @@ def parse_args() -> argparse.Namespace:
         metavar="PROFILE",
         help=f"Extra profiles to apply on top of base (available: {', '.join(extras)})",
     )
+    parser.add_argument(
+        "-f",
+        "--filter",
+        action="append",
+        metavar="PATH",
+        default=[],
+        dest="filters",
+        help=(
+            "Restrict the run to a single repo-relative path from the "
+            "selected profiles. Repeat to allow multiple paths. Skips "
+            "package and terminfo checks."
+        ),
+    )
     return parser.parse_args()
 
 
@@ -499,9 +532,13 @@ def main() -> int:
     ctx = Context(args)
     resolved = resolve_profiles(ctx, ["base", *args.profiles])
 
+    if args.filters:
+        resolved = apply_filter(ctx, resolved, args.filters)
+
     if args.remove_existing:
         remove_all_symlinks(ctx, resolved.symlinks, resolved.symlink_map)
     else:
+        if not args.filters:
             check_terminfo(ctx)
             check_packages_installed(ctx, resolved.pkgs)
         create_all_symlinks(ctx, resolved.symlinks, resolved.symlink_map)