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/sources.d/20-history.sh

@@ -3,9 +3,23 @@
 # typed and moved on from before (thefuck's history.py idea). Reads
 # HISTFILE directly since a separate process doesn't inherit the parent
 # shell's in-memory history.
+#
+# Single awk pass over the tail of the file: on weak/emulated hardware
+# every avoided fork+exec matters (measured: an unoptimized PATH walk in
+# 40-pathfuzzy.sh took >30s on this box before being fixed; pipeline
+# depth has the same tax, just smaller per-hop) -- a five-process
+# tail|grep|grep|awk|tail chain does the same job as one awk script
+# reading the file once.
 cmd="$1"
 first_word=$(printf '%s' "$cmd" | awk '{print $1}')
 [ -n "$first_word" ] || exit 0
 hf="${HISTFILE:-$HOME/.bash_history}"
 [ -r "$hf" ] || exit 0
-tail -n 300 "$hf" 2>/dev/null | grep -F -- "$first_word " | grep -vF -- "$cmd" | awk '!seen[$0]++' | tail -5
+
+tail -n 300 "$hf" 2>/dev/null | awk -v first="$first_word" -v full="$cmd" '
+index($0, first " ") == 1 && $0 != full && !seen[$0]++ { buf[++n] = $0 }
+END {
+    start = (n > 5) ? n - 4 : 1
+    for (i = start; i <= n; i++) print buf[i]
+}
+'

contrib/fx/sources.d/30-selfdiag.sh

@@ -12,6 +12,11 @@
 # correctly across branches/arguments in practice. One taught fix this
 # way covers every future self-diagnosing failure from that program, not
 # just the one instance that happened to trigger the teaching prompt.
+#
+# The emitted function runs on every future call to that program for
+# the rest of the session, so its own internal extraction is one awk
+# pass, not a grep|sed|tail chain -- three fewer forks on every failure
+# it ever handles, not just this first one.
 cmd="$1"
 prog=$(printf '%s' "$cmd" | awk '{print $1}')
 [ -n "$prog" ] || exit 0
@@ -19,5 +24,5 @@ prog=$(printf '%s' "$cmd" | awk '{print $1}')
 printf '%s\n' "$FX_OUTPUT" | grep -qE "^[[:space:]]*${prog}[[:space:]]" || exit 0
 
 cat <<FIX
-${prog}(){ out=\$(command ${prog} "\$@" 2>&1); ec=\$?; if [ \$ec -ne 0 ]; then sug=\$(printf '%s\\n' "\$out" | grep -E "^[[:space:]]*${prog}[[:space:]]" | sed 's/^[[:space:]]*//' | tail -1); if [ -n "\$sug" ]; then eval "command \$sug"; return \$?; fi; fi; printf '%s\\n' "\$out"; return \$ec; }
+${prog}(){ out=\$(command ${prog} "\$@" 2>&1); ec=\$?; if [ \$ec -ne 0 ]; then sug=\$(printf '%s\\n' "\$out" | awk '/^[ \\t]*${prog}[ \\t]/{sub(/^[ \\t]*/,""); s=\$0} END{print s}'); if [ -n "\$sug" ]; then eval "command \$sug"; return \$?; fi; fi; printf '%s\\n' "\$out"; return \$ec; }
 FIX

contrib/fx/sources.d/40-pathfuzzy.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 # PATH-fuzzy source: if the first word isn't a known command, alias, or
 # function, offer a function wrapping the closest-spelled real command
 # as a candidate -- as a fix you approve through the normal f() flow,
@@ -7,6 +7,12 @@
 # otherwise), so an alias-based fix silently does nothing when f/fx run
 # inside a script.
 #
+# Pure POSIX: walks $PATH directly instead of `compgen -c`, which is a
+# bash-only builtin and does not exist under busybox ash -- this source
+# used to be dead weight on exactly the minimal/embedded shells this
+# project targets. Tested against busybox ash + busybox awk directly,
+# not just bash + gawk.
+#
 # Uses Damerau-Levenshtein-lite (edit distance + adjacent transposition)
 # so the canonical "gti" -> "git" typo scores 1, not 2 -- plain Hamming
 # or substitution-only distance ties it with unrelated 3-letter commands
@@ -15,9 +21,11 @@ cmd="$1"
 first_word=$(printf '%s' "$cmd" | awk '{print $1}')
 [ -n "$first_word" ] || exit 0
 command -v "$first_word" >/dev/null 2>&1 && exit 0
-type "$first_word" >/dev/null 2>&1 && exit 0
 
-compgen -c 2>/dev/null | sort -u | awk -v target="$first_word" '
+IFS=:
+for d in $PATH; do
+    ls "$d" 2>/dev/null
+done | sort -u | awk -v target="$first_word" '
 function min3(a, b, c) { return (a < b ? (a < c ? a : c) : (b < c ? b : c)) }
 function distance(a, b,    n, m, i, j, ca, cb, cost, tmp) {
     n = length(a); m = length(b)