Bug where a pipe might call the cb twice. Reported by russell_h in IRC.

lib/utils/exec.js

@@ -30,16 +30,19 @@ function exec (cmd, args, env, takeOver, cb) {
 function logger (d) { if (d) process.binding("stdio").writeError(d+"") }
 function pipe (cp1, cp2, cb) {
   sys.pump(cp1.stdout, cp2.stdin)
+  var errState = null
   if (log.level <= log.LEVEL.silly) {
     cp1.stderr.on("data", logger)
     cp2.stderr.on("data", logger)
   }
   cp1.on("exit", function (code) {
     if (!code) return log.verbose(cp2.name || "<unknown>", "success")
     cp2.kill()
-    cb(new Error( "Failed "+(cp1.name || "<unknown>")+"\nexited with "+code))
+    cb(errState = new Error(
+      "Failed "+(cp1.name || "<unknown>")+"\nexited with "+code))
   })
   cp2.on("exit", function (code) {
+    if (errState) return
     if (!code) return log.verbose(cp1.name || "<unknown>", "success", cb)
     cb(new Error( "Failed "+(cp2.name || "<unknown>")+"\nexited with "+code))
   })

package.json

@@ -1,6 +1,6 @@
 { "name" : "npm"
 , "description" : "A package manager for node"
-, "version" : "0.1.27-2"
+, "version" : "0.1.27-3"
 , "homepage" : "http://npmjs.org/"
 , "author" : "Isaac Z. Schlueter <[email protected]> (http://blog.izs.me)"
 , "contributors" :