Add sign-git-tag config for 'npm version' command

doc/cli/config.md

@@ -694,6 +694,17 @@ character to indicate reverse sort.
 
 The shell to run for the `npm explore` command.
 
+### sign-git-tag
+
+* Default: false
+* Type: Boolean
+
+If set to true, then the `npm version` command will tag the version
+using `-s` to add a signature.
+
+Note that git requires you to have set up GPG keys in your git configs
+for this to work properly.
+
 ### strict-ssl
 
 * Default: true

lib/utils/config-defs.js

@@ -189,6 +189,7 @@ Object.defineProperty(exports, "defaults", {get: function () {
     , searchexclude: null
     , searchsort: "name"
     , shell : osenv.shell()
+    , "sign-git-tag": false
     , "strict-ssl": true
     , tag : "latest"
     , tmp : temp
@@ -280,6 +281,7 @@ exports.types =
                 , "date", "-date"
                 , "keywords", "-keywords" ]
   , shell : String
+  , "sign-git-tag": Boolean
   , "strict-ssl": Boolean
   , tag : String
   , tmp : path

lib/version.js

@@ -10,7 +10,7 @@ var exec = require("./utils/exec.js")
   , log = require("npmlog")
   , npm = require("./npm.js")
 
-version.usage = "npm version <newversion> [--message commit-message]"
+version.usage = "npm version [<newversion> | major | minor | patch | build]\n"
               + "\n(run in package dir)\n"
               + "'npm -v' or 'npm --version' to print npm version "
               + "("+npm.version+")\n"
@@ -52,19 +52,23 @@ function checkGit (data, cb) {
       , function (er, code, stdout, stderr) {
     var lines = stdout.trim().split("\n").filter(function (line) {
       return line.trim() && !line.match(/^\?\? /)
+    }).map(function (line) {
+      return line.trim()
     })
     if (lines.length) return cb(new Error(
       "Git working directory not clean.\n"+lines.join("\n")))
     write(data, function (er) {
       if (er) return cb(er)
       var message = npm.config.get("message").replace(/%s/g, data.version)
+        , sign = npm.config.get("sign-git-tag")
+        , flag = sign ? "-sm" : "-am"
       chain
         ( [ [ exec, npm.config.get("git")
             , ["add","package.json"], process.env, false ]
           , [ exec, npm.config.get("git")
             , ["commit", "-m", message ], process.env, false ]
           , [ exec, npm.config.get("git")
-            , ["tag", "v"+data.version], process.env, false ] ]
+            , ["tag", "v"+data.version, flag, message], process.env, false ] ]
         , cb )
     })
   })