allow run jobs in parallel (nodenv#13)

Closes: nodenv#13

bin/nodenv-each

@@ -2,14 +2,15 @@
 #
 # Summary: Execute a command for each Node version
 #
-# Usage: nodenv each [-g] [-v] [--] <command> [arg1 arg2...]
+# Usage: nodenv each [-g] [-p] [-v] [--] <command> [arg1 arg2...]
 #
 # Executes a command for each Node version by setting NODENV_VERSION.
 # Failures are collected and reported at the end.
 #
 # Options:
 #   --help, -h      Show help/usage
 #   --system, -g    Include the system `node`.
+#   --parallel -p   Run everything in parallel.
 #   --verbose, -v   Verbose mode. Prints a header for each node.
 #
 set -e
@@ -32,6 +33,9 @@ for arg in "$@"; do
     -g | --system )
       include_system=1
       ;;
+    -p | --parallel )
+      parallel=1
+      ;;
     -v | --verbose )
       verbose=1
       ;;
@@ -53,6 +57,13 @@ if [ $# -eq 0 ]; then
   exit 1
 fi
 
+if [ -n "$parallel" ]; then
+    if ! command -v parallel &> /dev/null; then
+        echo "You must install the parallel tool in order to run jobs in parallel"
+        exit 1
+    fi
+fi
+
 GRAY=""
 RED=""
 YELLOW=""
@@ -69,21 +80,32 @@ failed_nodes=""
 
 trap "exit 1" INT
 
-for node in ${include_system:+system} $(nodenv-versions --bare --skip-aliases); do
+exec_node() {
   if [ -n "$verbose" ]; then
-    header="===[$node]==================================================================="
-    header="${header:0:72}"
-    header="${header/[/[${YELLOW}}"
-    header="${header/]/${GRAY}]}"
+    local header="===[$1]==================================================================="
+    local header="${header:0:72}"
+    local header="${header/[/[${YELLOW}}"
+    local header="${header/]/${GRAY}]}"
     echo -e "${GRAY}${header}${NORMAL}"
   fi
-
-  NODENV_VERSION="$node" "$@" || failed_nodes="$failed_nodes $node"
-
+  local version="$1"
+  shift
+  NODENV_VERSION="$version" "$@"
   [ -n "$verbose" ] && echo
-done
+}
 
-if [ -n "$failed_nodes" ]; then
-  echo -e "${RED}FAILED IN:${failed_nodes}${NORMAL}"
-  exit 1
+NODES=(${include_system:+system} $(nodenv-versions --bare --skip-aliases))
+
+if [ -n "$parallel" ]; then
+    export -f exec_node
+    export verbose YELLOW GRAY NORMAL
+    echo "${NODES[@]}" | tr ' ' '\n' | parallel --env YELLOW --env GRAY --env NORMAL --env verbose --env exec_node exec_node {0} "$@"
+else
+    for node in "${NODES[@]}"; do
+        NODENV_VERSION="$node" "$@" || failed_nodes="$failed_nodes $node"
+    done
+    if [ -n "$failed_nodes" ]; then
+        echo -e "${RED}FAILED IN:${failed_nodes}${NORMAL}"
+        exit 1
+    fi
 fi