Adding `nvm exec` command.

README.markdown

@@ -38,7 +38,7 @@ Often I also put in a line to use a specific version of node.
 ## Usage
 
 You can create an `.nvmrc` file containing version number in the project root directory (or any parent directory).
-`nvm use`, `nvm install`, and `nvm run` will all respect an `.nvmrc` file.
+`nvm use`, `nvm install`, `nvm exec`, and `nvm run` will all respect an `.nvmrc` file.
 
 To download, compile, and install the latest v0.10.x release of node, do this:
 
@@ -52,6 +52,10 @@ Or you can just run it:
 
     nvm run 0.10 --version
 
+Or, you can run any arbitrary command in the node environment:
+
+    nvm exec 0.10 node --version
+
 If you want to see what versions are installed:
 
     nvm ls

nvm.sh

@@ -639,6 +639,29 @@ nvm() {
       echo "Running node $VERSION"
       NODE_PATH=$RUN_NODE_PATH $NVM_DIR/$VERSION/bin/node "$@"
     ;;
+    "exec" )
+      shift
+
+      local provided_version
+      provided_version=$1
+      if [ -n "$provided_version" ]; then
+        VERSION=`nvm_version $provided_version`
+        if [ $VERSION = "N/A" ]; then
+          provided_version=''
+          nvm_rc_version
+          VERSION=`nvm_version $NVM_RC_VERSION`
+        else
+          shift
+        fi
+      fi
+
+      if [ ! -d "$NVM_DIR/$VERSION" ]; then
+        echo "$VERSION version is not installed yet" >&2
+        return 1
+      fi
+      echo "Running node $VERSION"
+      NODE_VERSION=$VERSION $NVM_DIR/nvm-exec "$@"
+    ;;
     "ls" | "list" )
       local NVM_LS_OUTPUT
       local NVM_LS_EXIT_CODE