npx: bundle npx with npm itself

npx is an npm package runner with a bunch of nice features. While
it is also available on the npm registry as `npx`, it's the sort
of thing that's better off being bundles with npm itself.

Fixes: npm#6053
PR-URL: npm/npm#17685
Credit: @zkat
Reviewed-By: @iarna

Makefile

@@ -14,7 +14,8 @@ html_docdeps = html/dochead.html \
 cli_mandocs = $(shell find doc/cli -name '*.md' \
                |sed 's|.md|.1|g' \
                |sed 's|doc/cli/|man/man1/|g' ) \
-               man/man1/npm-README.1
+               man/man1/npm-README.1 \
+               man/man1/npx.1
 
 files_mandocs = $(shell find doc/files -name '*.md' \
                |sed 's|.md|.5|g' \
@@ -96,6 +97,9 @@ man/man1/%.1: doc/cli/%.md scripts/doc-build.sh package.json
 	@[ -d man/man1 ] || mkdir -p man/man1
 	scripts/doc-build.sh $< $@
 
+man/man1/npx.1: node_modules/libnpx/libnpx.1
+	cat $< | sed s/libnpx/npx/ > $@
+
 man/man5/npm-json.5: man/man5/package.json.5
 	cp $< $@
 

bin/npx

@@ -0,0 +1,34 @@
+#!/bin/sh
+(set -o igncr) 2>/dev/null && set -o igncr; # cygwin encoding fix
+
+basedir=`dirname "$0"`
+
+case `uname` in
+    *CYGWIN*) basedir=`cygpath -w "$basedir"`;;
+esac
+
+NODE_EXE="$basedir/node.exe"
+if ! [ -x "$NODE_EXE" ]; then
+  NODE_EXE=node
+fi
+
+NPX_CLI_JS="$basedir/node_modules/npm/bin/npx-cli.js"
+
+case `uname` in
+  *MINGW*)
+    NPM_PREFIX=`"$NODE_EXE" "$NPX_CLI_JS" prefix -g`
+    NPM_PREFIX_NPX_CLI_JS="$NPM_PREFIX/node_modules/npm/bin/npx-cli.js"
+    if [ -f "$NPM_PREFIX_NPX_CLI_JS" ]; then
+      NPX_CLI_JS="$NPM_PREFIX_NPX_CLI_JS"
+    fi
+    ;;
+  *CYGWIN*)
+    NPM_PREFIX=`"$NODE_EXE" "$NPX_CLI_JS" prefix -g`
+    NPM_PREFIX_NPX_CLI_JS="$NPM_PREFIX/node_modules/npm/bin/npx-cli.js"
+    if [ -f "$NPM_PREFIX_NPX_CLI_JS" ]; then
+      NPX_CLI_JS="$NPM_PREFIX_NPX_CLI_JS"
+    fi
+    ;;
+esac
+
+"$NODE_EXE" "$NPX_CLI_JS" "$@"

bin/npx-cli.js

@@ -0,0 +1,8 @@
+#!/usr/bin/env node
+
+const npx = require('libnpx')
+const path = require('path')
+
+const NPM_PATH = path.join(__dirname, 'npm-cli.js')
+
+npx(npx.parseArgs(process.argv, NPM_PATH))

bin/npx.cmd

@@ -0,0 +1,19 @@
+:: Created by npm, please don't edit manually.
+@ECHO OFF
+
+SETLOCAL
+
+SET "NODE_EXE=%~dp0\node.exe"
+IF NOT EXIST "%NODE_EXE%" (
+  SET "NODE_EXE=node"
+)
+
+SET "NPX_CLI_JS=%~dp0\node_modules\npm\bin\npx-cli.js"
+FOR /F "delims=" %%F IN ('CALL "%NODE_EXE%" "%NPX_CLI_JS%" prefix -g') DO (
+  SET "NPM_PREFIX_NPX_CLI_JS=%%F\node_modules\npm\bin\npx-cli.js"
+)
+IF EXIST "%NPM_PREFIX_NPX_CLI_JS%" (
+  SET "NPX_CLI_JS=%NPM_PREFIX_NPX_CLI_JS%"
+)
+
+"%NODE_EXE%" "%NPX_CLI_JS%" %*