Enable ShellCheck rules

Enabled ShellCheck rules:
  SC1087
  SC2001
  SC2004
  SC2005
  SC2006
  SC2016
  SC2028
  SC2048
  SC2066 (note that IFS already contains only a line feed)
  SC2116
  SC2166
  SC2181
  SC2206
  SC2207
  SC2230
  SC2236

(cherry picked from commit bitcoin/bitcoin@1ac454a384)

Zcash: Applies more of this commit. It was partially backported in
zcash/zcash#4827, and is also partially backported here for the scripts
we actually have.

autogen.sh

@@ -13,6 +13,6 @@ if [ -z ${LIBTOOLIZE} ] && GLIBTOOLIZE="$(command -v glibtoolize)"; then
   LIBTOOLIZE="${GLIBTOOLIZE}"
   export LIBTOOLIZE
 fi
-which autoreconf >/dev/null || \
+command -v autoreconf >/dev/null || \
   (echo "configuration failed, please install autoconf first" && exit 1)
 autoreconf --install --force --warnings=all

contrib/qos/tc.sh

@@ -33,7 +33,7 @@ tc class add dev ${IF} parent 1:1 classid 1:11 htb rate ${LIMIT} ceil ${LIMIT} p
 tc filter add dev ${IF} parent 1: protocol ip prio 1 handle 1 fw classid 1:10
 tc filter add dev ${IF} parent 1: protocol ip prio 2 handle 2 fw classid 1:11
 
-if [ ! -z "${LOCALNET_V6}" ] ; then
+if [ -n "${LOCALNET_V6}" ] ; then
 	# v6 cannot have the same priority value as v4
 	tc filter add dev ${IF} parent 1: protocol ipv6 prio 3 handle 1 fw classid 1:10
 	tc filter add dev ${IF} parent 1: protocol ipv6 prio 4 handle 2 fw classid 1:11
@@ -56,7 +56,7 @@ fi
 iptables -t mangle -A OUTPUT -p tcp -m tcp --dport 8233 ! -d ${LOCALNET_V4} -j MARK --set-mark 0x2
 iptables -t mangle -A OUTPUT -p tcp -m tcp --sport 8233 ! -d ${LOCALNET_V4} -j MARK --set-mark 0x2
 
-if [ ! -z "${LOCALNET_V6}" ] ; then
+if [ -n "${LOCALNET_V6}" ] ; then
 	ip6tables -t mangle -A OUTPUT -p tcp -m tcp --dport 8233 ! -d ${LOCALNET_V6} -j MARK --set-mark 0x4
 	ip6tables -t mangle -A OUTPUT -p tcp -m tcp --sport 8233 ! -d ${LOCALNET_V6} -j MARK --set-mark 0x4
 fi

share/genbuild.sh

@@ -26,7 +26,7 @@ git_check_in_repo() {
 
 DESC=""
 SUFFIX=""
-if [ "${BITCOIN_GENBUILD_NO_GIT}" != "1" -a -e "$(which git 2>/dev/null)" -a "$(git rev-parse --is-inside-work-tree 2>/dev/null)" = "true" ] && git_check_in_repo share/genbuild.sh; then
+if [ "${BITCOIN_GENBUILD_NO_GIT}" != "1" ] && [ -e "$(command -v git)" ] && [ "$(git rev-parse --is-inside-work-tree 2>/dev/null)" = "true" ] && git_check_in_repo share/genbuild.sh; then
     # clean 'dirty' status of touched files that haven't been modified
     git diff >/dev/null 2>/dev/null
 

test/lint/lint-shell.sh

@@ -24,25 +24,9 @@ fi
 
 # Disabled warnings:
 disabled=(
-    SC1087 # Use braces when expanding arrays, e.g. ${array[idx]} (or ${var}[.. to quiet).
-    SC2001 # See if you can use ${variable//search/replace} instead.
-    SC2004 # $/${} is unnecessary on arithmetic variables.
-    SC2005 # Useless echo? Instead of 'echo $(cmd)', just use 'cmd'.
-    SC2006 # Use $(..) instead of legacy `..`.
-    SC2016 # Expressions don't expand in single quotes, use double quotes for that.
-    SC2028 # echo won't expand escape sequences. Consider printf.
     SC2046 # Quote this to prevent word splitting.
-    SC2048 # Use "$@" (with quotes) to prevent whitespace problems.
-    SC2066 # Since you double quoted this, it will not word split, and the loop will only run once.
     SC2086 # Double quote to prevent globbing and word splitting.
-    SC2116 # Useless echo? Instead of 'cmd $(echo foo)', just use 'cmd foo'.
     SC2162 # read without -r will mangle backslashes.
-    SC2166 # Prefer [ p ] {&&,||} [ q ] as [ p -{a,o} q ] is not well defined.
-    SC2181 # Check exit code directly with e.g. 'if mycmd;', not indirectly with $?.
-    SC2206 # Quote to prevent word splitting, or split robustly with mapfile or read -a.
-    SC2207 # Prefer mapfile or read -a to split command output (or quote to avoid splitting).
-    SC2230 # which is non-standard. Use builtin 'command -v' instead.
-    SC2236 # Don't force -n instead of ! -z.
 )
 shellcheck -e "$(IFS=","; echo "${disabled[*]}")" \
     $(git ls-files -- "*.sh")