Fix real hardware/busybox breakage: dead compgen dependency, unreliable sourced-path detection, and fork-heavy pipelines in fx sources; verified against busybox ash+awk directly

contrib/fx/fx.sh

@@ -12,8 +12,15 @@
 #   fx some-command --that --might --fail
 #
 # Env vars:
-#   FX_SOURCES_DIR   override the sources directory (default: sources.d
-#                    next to this script)
+#   FX_SOURCES_DIR   the sources directory. Defaults to ./contrib/fx/sources.d
+#                    (i.e. source this file from the repo root). There is no
+#                    portable way for a *sourced* POSIX shell file to learn
+#                    its own path -- $0 is the enclosing shell's name, and
+#                    bash's BASH_SOURCE has no equivalent in dash/ash, so
+#                    this does not try to be clever about it. Anything
+#                    other than "source from repo root" (a different cwd,
+#                    a temp dir a la bootstrap.sh) must set this explicitly
+#                    *before* sourcing this file.
 #   FX_AUTO          if set, auto-pick the top candidate instead of
 #                    showing a picker
 #   FX_NO_PROBE      if set, skip fx's own diagnostic run of the command
@@ -32,14 +39,17 @@
 # Adding a source: drop a new executable file in sources.d/ that follows
 # the contract above. Nothing else to register or edit.
 
-# $0 is the enclosing shell's name when this file is *sourced*, not this
-# file's own path -- ${BASH_SOURCE[0]} is reliable under bash; for other
-# POSIX shells, set FX_SOURCES_DIR explicitly before sourcing this file.
-_fx_self="${BASH_SOURCE:-$0}"
-FX_SOURCES_DIR="${FX_SOURCES_DIR:-$(CDPATH= cd -- "$(dirname -- "$_fx_self")" 2>/dev/null && pwd)/sources.d}"
-unset _fx_self
+# Resolved to an absolute path *now*, at source time -- a relative
+# default would silently re-resolve against whatever cwd happens to be
+# active later when fx() is actually called, which is almost never the
+# repo root in practice.
+FX_SOURCES_DIR="${FX_SOURCES_DIR:-$(pwd)/contrib/fx/sources.d}"
 
 fx() {
+    if [ ! -d "$FX_SOURCES_DIR" ]; then
+        echo "fx: FX_SOURCES_DIR '$FX_SOURCES_DIR' not found -- no sources will fire." >&2
+        echo "fx: set FX_SOURCES_DIR before sourcing fx.sh if not running from the repo root." >&2
+    fi
     cmd="$*"
 
     FX_OUTPUT=""
@@ -55,7 +65,7 @@ fx() {
     candidates=$(
         for src in "$FX_SOURCES_DIR"/*; do
             [ -x "$src" ] || continue
-            label=$(basename "$src")
+            label="${src##*/}"
             "$src" "$cmd" 2>/dev/null | while IFS= read -r line; do
                 [ -n "$line" ] && printf '[%s] %s\n' "$label" "$line"
             done