Don't try to copy npm itself with nvm copy-packages.

Fixes #504.

nvm.sh

@@ -783,7 +783,7 @@ nvm() {
 
  # declare local INSTALLS first, otherwise it doesn't work in zsh
  local INSTALLS
- INSTALLS=$(nvm use $VERSION > /dev/null && npm list --global --parseable --depth=0 2> /dev/null | tail -n +2 | \grep -o -e '/[^/]*$' | cut -c 2- | xargs)
+ INSTALLS=$(nvm use $VERSION > /dev/null && npm list --global --parseable --depth=0 2> /dev/null | tail -n +2 | \grep -o -e '/[^/]*$' | cut -c 2- | \grep -v npm | xargs)
 
  npm install -g --quiet $INSTALLS
  ;;

test/slow/nvm copy-packages/should work as expected

@@ -6,15 +6,15 @@ die () { echo "$@" ; exit 1; }
 
 nvm use 0.10.28
 
-EXPECTED_PACKAGES="autoprefixer bower david eslint grunt-cli grunth-cli http-server jshint marked node-gyp npm recursive-blame uglify-js yo"
+EXPECTED_PACKAGES="autoprefixer bower david eslint grunt-cli grunth-cli http-server jshint marked node-gyp recursive-blame uglify-js yo"
 
 npm install -g --quiet $EXPECTED_PACKAGES
 
 nvm use 0.10.29
-ORIGINAL_PACKAGES=$(npm list --global --parseable --depth=0 2> /dev/null | tail -n +2 | grep -o -e '/[^/]*$' | cut -c 2- | sort | uniq | xargs)
+ORIGINAL_PACKAGES=$(npm list --global --parseable --depth=0 2> /dev/null | tail -n +2 | \grep -o -e '/[^/]*$' | cut -c 2- | \grep -v npm | sort | uniq | xargs)
 
 nvm copy-packages 0.10.28
-FINAL_PACKAGES=$(npm list --global --parseable --depth=0 2> /dev/null | tail -n +2 | grep -o -e '/[^/]*$' | cut -c 2- | sort | uniq | xargs)
+FINAL_PACKAGES=$(npm list --global --parseable --depth=0 2> /dev/null | tail -n +2 | \grep -o -e '/[^/]*$' | cut -c 2- | \grep -v npm | sort | uniq | xargs)
 
 [ "$FINAL_PACKAGES" = "$EXPECTED_PACKAGES" ] || die "final packages ($FINAL_PACKAGES) did not match expected packages ($EXPECTED_PACKAGES)"
 [ "$ORIGINAL_PACKAGES" != "$FINAL_PACKAGES" ] || die "original packages matched final packages ($ORIGINAL_PACKAGES)"