Move docs from book/ to docs/ (#8469)

automerge

docs/build-cli-usage.sh

@@ -0,0 +1,34 @@
+#!/usr/bin/env bash
+set -e
+
+cd "$(dirname "$0")"
+
+usage=$(cargo -q run -p solana-cli -- -C ~/.foo --help | sed 's|'"$HOME"'|~|g')
+
+out=${1:-src/cli/usage.md}
+
+cat src/cli/.usage.md.header > "$out"
+
+section() {
+  declare mark=${2:-"###"}
+  declare section=$1
+  read -r name rest <<<"$section"
+
+  printf '%s %s
+' "$mark" "$name"
+  printf '```text
+%s
+```
+
+' "$section"
+}
+
+section "$usage" >> "$out"
+
+in_subcommands=0
+while read -r subcommand rest; do
+  [[ $subcommand == "SUBCOMMANDS:" ]] && in_subcommands=1 && continue
+  if ((in_subcommands)); then
+      section "$(cargo -q run -p solana-cli -- help "$subcommand" | sed 's|'"$HOME"'|~|g')" "####" >> "$out"
+  fi
+done <<<"$usage">>"$out"