feat(fish): add remote deploy helper

AGENTS.md

@@ -101,3 +101,5 @@ The domain model (Host, Module, Skeleton, Auto-loader, Enable convention, overla
   Keep fractional scaling sharp with Hyprland's `xwayland.force_zero_scaling` and Steam's own `STEAM_FORCE_DESKTOPUI_SCALING` instead.
 - AdGuard's LAN wildcard rewrite for `*.alexion.dev` points names at the reverse-proxy guest, including non-HTTP ports.
   Keep `git.alexion.dev:2022` working by proxying that TCP stream through the reverse-proxy guest to Gitea.
+- Remote deploy helpers that run target-side `sudo` over SSH need a TTY.
+  Use `ssh -t` unless the target command is guaranteed not to prompt for sudo credentials.

modules/fish/fish.nix

@@ -120,6 +120,11 @@ in
             description = "Copy a file, or recursively copy a source directory into a destination";
             body = builtins.readFile ./functions/copy.fish;
           };
+
+          deploy-to = {
+            description = "Deploy the current dotfiles branch to a host through target-local nixos-rebuild";
+            body = builtins.readFile ./functions/deploy-to.fish;
+          };
         };
 
         # Rendered by home-manager into ~/.config/fish/config.fish.

modules/fish/functions/deploy-to.fish

@@ -0,0 +1,53 @@
+if test (count $argv) -lt 1; or test (count $argv) -gt 2
+    echo "usage: deploy-to <host> [branch]" >&2
+    return 2
+end
+
+set host $argv[1]
+set branch $argv[2]
+
+if test -z "$branch"
+    set branch (git branch --show-current)
+end
+
+if test -z "$branch"
+    echo "deploy-to: could not determine the current branch" >&2
+    return 2
+end
+
+git rev-parse --show-toplevel >/dev/null 2>&1
+or begin
+    echo "deploy-to: run this from a git checkout" >&2
+    return 2
+end
+
+set dirty_lines (git status --porcelain)
+if test (count $dirty_lines) -gt 0
+    echo "deploy-to: refusing to deploy with a dirty local worktree" >&2
+    return 1
+end
+
+git fetch origin
+or return $status
+
+set remote_ref refs/remotes/origin/$branch
+git rev-parse --verify --quiet $remote_ref >/dev/null
+or begin
+    echo "deploy-to: origin/$branch does not exist" >&2
+    return 1
+end
+
+set local_head (git rev-parse HEAD)
+set remote_head (git rev-parse $remote_ref)
+
+if test "$local_head" != "$remote_head"
+    echo "deploy-to: local HEAD differs from origin/$branch" >&2
+    echo "deploy-to: push or reset the branch before deploying" >&2
+    return 1
+end
+
+set escaped_branch (string escape -- $branch)
+set escaped_host (string escape -- $host)
+set remote_command "cd ~/wrk/dotfiles && git fetch origin && git switch -- $escaped_branch && git reset --hard origin/$escaped_branch && sudo nixos-rebuild switch --flake .#$escaped_host --print-build-logs"
+
+ssh -t $host $remote_command