changed requests batch size to 8 by default instead of number of cpus

added cli option to override this batch size
	modified:   bin/ncu
	modified:   lib/versionmanager.js

bin/ncu

@@ -46,6 +46,7 @@ program
     .option('-t, --greatest', 'find the highest versions available instead of the latest stable versions')
     .option('--timeout <ms>', 'a global timeout in ms')
     .option('-u, --upgrade', 'overwrite package file')
+    .option('--requests-batch-size <n>','requests to npm registry are issued in batches whose size is determined by this option',parseInt,8)
     .option('-x, --reject <matches>', 'exclude packages matching the given string, comma-or-space-delimited list, or /regex/')
     .option('-v, --version', pkg.version, () => {
         console.log(pkg.version);

lib/versionmanager.js

@@ -8,7 +8,6 @@ const versionUtil = require('./version-util.js');
 const packageManagers = require('./package-managers');
 const prompts = require('prompts');
 const pMap = require('p-map');
-const os = require('os');
 // keep order for setPrecision
 const DEFAULT_WILDCARD = '^';
 
@@ -256,7 +255,8 @@ function upgradePackageDefinitions(currentDependencies, options) {
         json: options.json,
         loglevel: options.loglevel,
         enginesNode: options.enginesNode,
-        timeout: options.timeout
+        timeout: options.timeout,
+        batchSize: options.requestsBatchSize
     }).then(latestVersions => {
 
         const upgradedDependencies = upgradeDependencies(currentDependencies, latestVersions, {
@@ -456,8 +456,7 @@ function queryVersions(packageMap, options = {}) {
             return cint.keyValue(packageList[i], version);
         });
     }
-
-    return pMap(packageList,getPackageVersionProtected,{concurrency: os.cpus().length})
+    return pMap(packageList,getPackageVersionProtected,{concurrency: options.batchSize})
         .then(zipVersions)
         .then(_.partialRight(_.pickBy, _.identity));
 }
@@ -562,5 +561,6 @@ module.exports = {
     isUpgradeable,
     queryVersions,
     upgradeDependencies,
-    upgradeDependencyDeclaration
+    upgradeDependencyDeclaration,
+    getPackageManager
 };