Installer: cleanup of restart-check, --clone and the uninstall changes

- uninstall: nix-installer's copy outside /nix is made and run as root
  (a user-writable copy run by sudo could be swapped); README uninstall
  paragraph shortened to one account of what happens when Nix stays.
- session.nix: the restart-check activation after steamFrameUserServices,
  so the latter's comment is above it again.
- install.sh: a duplicate `local` in port_listening; comments.
- docs/cleanup.md: the installer internals of --clone (how an existing
  clone is recognised, which git) and restart-check (what it compares,
  test overrides); README keeps the usage.
- README install paragraph: shorter list of the dashboard patches.

README.md

@@ -84,11 +84,10 @@ runs `home-manager switch`; what it sets up is listed under
 [Set up by install.sh](#set-up-by-installsh). Everything works in the running
 session right away, except two settings read only at a process start: the
 [keyboard layout](docs/session.md#keyboard-layout) (next Steam session start)
-and the [SteamVR dashboard patches](docs/steamvr-debugger.md) (VR pet, the VR
-keyboard's suggestion strip, window curvature and the other patches of
-SteamVR's dashboard; next SteamVR start). If you use them, the installer ends
-with "Restart once": reboot once. Re-running it just switches
-again (`--yes` answers every question). Afterwards edit
+and the [SteamVR dashboard patches](docs/steamvr-debugger.md) (VR pet, VR
+keyboard suggestions, window curvature, ...; next SteamVR start). If they
+are waiting, the installer ends with "Restart once": reboot once. Re-running
+it just switches again (`--yes` answers every question). Afterwards edit
 `~/nix-config/home.nix` and switch (see [Usage](#usage)).
 
 Your own config in a git repository: `--clone <git-url>` clones it into
@@ -501,12 +500,11 @@ stops Home Manager's user services (reverting the UI patches), runs
 `cleanup --all`, runs `home-manager uninstall`, then removes Nix and the
 per-user Nix state (see [Set up by install.sh](#set-up-by-installsh)). If
 SteamVR is running, its key is restored when SteamVR stops (the closing
-message says so). Programs started from the Nix store keep `/nix` busy:
-before removing Nix, `uninstall` lists them and waits until you close them
-(with `--yes`, it stops instead); close them or run it right after a reboot.
-If Nix's own uninstaller fails anyway, the rest still runs (the `~/.config/home-manager` link goes) except
-the per-user Nix state, and the closing message says to reboot and run
-`uninstall` again. Your configuration, `*.hm-backup-*` files, app data and
+message says so). Nix can't be removed while programs started from the Nix
+store run: `uninstall` lists them and waits; close them or run it right
+after a reboot. If Nix stays (in use, `--yes`, or its uninstaller failed),
+the rest still runs (the `~/.config/home-manager` link goes) except the
+per-user Nix state, and the closing message says to run `uninstall` again. Your configuration, `*.hm-backup-*` files, app data and
 Flatpaks stay.
 
 To drop steam-frame-nix from a Home Manager configuration you keep, first

docs/cleanup.md

@@ -45,6 +45,21 @@ What `install.sh install` sets up is listed in the README under
 desktop can't reach it with its own environment) and uses the installed
 `home-manager` if there is one, else Home Manager's `master`.
 
+`install --clone` takes SteamOS' `git`, else `nix run nixpkgs#git`. An
+existing directory is reused only if it is the top of a clone whose
+`origin` is the same repository: URLs are compared as lower-case
+host/path without `.git` (so `git@host:o/r`, `ssh://git@host/o/r` and
+`https://host/o/r.git` match), and with `--ref` it must be on that branch.
+
+`restart-check` (run by the session module's activation after
+`steamFrameUserServices`, and by `install` at its end) compares the
+keyboard layout drop-in on `gamescope-session.service` with
+`XKB_DEFAULT_*` in the environment of the first readable process in that
+unit's cgroup (gamescope's own isn't readable), and, while SteamVR runs
+with the debugger drop-in, looks for a listener on port 8087 in
+`/proc/net/tcp*`. Tests use `STEAM_FRAME_NIX_PROC` and
+`STEAM_FRAME_NIX_CGROUP` (section F of `modules/cleanup/check.nix`).
+
 `uninstall` removes Nix with nix-installer, which fails when it can't
 unmount `/nix` (`systemctl stop nix.mount`). Before that it scans `/proc`
 for processes using `/nix`: their `exe`, `cwd`, `root` or an `fd` links into
@@ -56,6 +71,6 @@ the script itself, its subshells (descendants) and its process group (the
 `uninstall` from another terminal. Nothing is killed: it asks to close them
 and re-checks on Enter, or (`--yes`, no terminal) stops before Nix. A bash
 from the Nix store re-executes the script with `/usr/bin/bash` first, and
-nix-installer runs from a copy outside `/nix`. The check uses
+nix-installer runs from a root-owned copy in `/tmp`. The check uses
 `STEAM_FRAME_NIX_PROC` as a fake `/proc` (section H of
 `modules/cleanup/check.nix`).

install.sh

@@ -234,17 +234,19 @@ install_nix() {
 }
 
 uninstall_nix() {
-  local rc=0 bin
+  local rc=0 bin=
   need_sudo
   ro_unlock
   step "Uninstalling Nix"
-  # From a copy: the uninstaller running from /nix would keep /nix busy.
-  bin="$(mktemp)"
-  if ! { cp "$NIX_INSTALLER_BIN" "$bin" && chmod +x "$bin" && "$bin" --version >/dev/null 2>&1; }; then
-    rm -f "$bin"; bin=$NIX_INSTALLER_BIN
+  # From a root-owned copy: the uninstaller running from /nix would keep
+  # /nix busy.
+  if ! bin="$(sudo mktemp)" || ! sudo cp "$NIX_INSTALLER_BIN" "$bin" \
+     || ! sudo chmod 700 "$bin" || ! sudo "$bin" --version >/dev/null 2>&1; then
+    [[ -n $bin ]] && sudo rm -f "$bin"
+    bin=$NIX_INSTALLER_BIN
   fi
   sudo "$bin" uninstall --no-confirm || rc=$?
-  [[ $bin == "$NIX_INSTALLER_BIN" ]] || rm -f "$bin"
+  [[ $bin == "$NIX_INSTALLER_BIN" ]] || sudo rm -f "$bin"
   ro_relock
   return "$rc"
 }
@@ -1056,7 +1058,6 @@ session_xkb() { # LAYOUT|VARIANT
 
 # Whether something listens on 127.0.0.1/::1/any :<port> (/proc/net/tcp*).
 port_listening() { # port
-  local hex
   local hex f files=()
   printf -v hex '%04X' "$1"
   for f in "$SFN_PROC/net/tcp" "$SFN_PROC/net/tcp6"; do [[ -r $f ]] && files+=("$f"); done
@@ -1178,7 +1179,8 @@ nix_users() {
     grep -ls '[[:space:]]/nix/' "$SFN_PROC"/[0-9]*/maps || true
   } | while IFS= read -r p; do p=${p#"$SFN_PROC"/}; echo "${p%%/*}"; done | sort -un \
     | while read -r pid; do
-      [[ $pid != "$self" ]] && { read -r name <"$SFN_PROC/$pid/comm"; } 2>/dev/null || continue
+      [[ $pid != "$self" ]] || continue
+      { read -r name <"$SFN_PROC/$pid/comm"; } 2>/dev/null || continue   # exited
       # argv[0]'s name says more than comm (often a thread name)
       argv0=''; { IFS= read -r -d '' argv0 <"$SFN_PROC/$pid/cmdline"; } 2>/dev/null || true
       [[ ${argv0##*/} == '' || ${argv0##*/} == exe ]] || name=${argv0##*/}
@@ -1274,9 +1276,9 @@ cmd_uninstall() {
   cmd_cleanup --all
   remove_hm
 
-  # A failed Nix uninstall (e.g. /nix still busy) must not skip the rest:
-  # Home Manager is gone by now, so its config link goes regardless; the
-  # per-user Nix files stay for a Nix that may still be there.
+  # Nix still in use or a failed Nix uninstall must not skip the rest: Home
+  # Manager is gone by now, so its config link goes regardless; the per-user
+  # Nix files stay for the Nix that is still there.
   local nix_failed=''
   if (( ! keep_nix )); then
     if [[ -x $NIX_INSTALLER_BIN ]]; then

modules/session.nix

@@ -98,12 +98,6 @@ in {
 
   # In a subshell: the outer session's environment must not leak into
   # activation steps that run later.
-  # Read-only; a warning, never a failed switch.
-  config.home.activation.steamFrameRestartCheck = lib.hm.dag.entryAfter [ "steamFrameUserServices" ] ''
-    STEAM_FRAME_NIX_RUNTIME_DIR=${lib.escapeShellArg cfg.runtimeDir} XDG_CONFIG_HOME=${lib.escapeShellArg config.xdg.configHome} \
-      ${lib.getExe restartCheck} || true
-  '';
-
   config.home.activation.steamFrameUserServices = lib.hm.dag.entryAfter [ "reloadSystemd" ] (''
     (
     export XDG_RUNTIME_DIR=${lib.escapeShellArg cfg.runtimeDir} DBUS_SESSION_BUS_ADDRESS=${lib.escapeShellArg cfg.bus}
@@ -121,4 +115,10 @@ in {
   '' + ''
     )
   '');
+
+  # Read-only; a warning, never a failed switch.
+  config.home.activation.steamFrameRestartCheck = lib.hm.dag.entryAfter [ "steamFrameUserServices" ] ''
+    STEAM_FRAME_NIX_RUNTIME_DIR=${lib.escapeShellArg cfg.runtimeDir} XDG_CONFIG_HOME=${lib.escapeShellArg config.xdg.configHome} \
+      ${lib.getExe restartCheck} || true
+  '';
 }