Using the right git command generate clearer archives name in pkg.sh script

`git describe` outputs things like this
v1.0.4-14-g2414721
(taken from doc)

pkg.sh

@@ -9,9 +9,8 @@ if ! [ -e dist ]; then
 fi
 
 # If no tag, use commit SHA1
-tag=`git tag --points-at HEAD`
-id=`git rev-parse --short --verify HEAD`
-name=OcLaunch_${tag}-${id}.tgz
+id=`git describe HEAD`
+name=OcLaunch_${id}.tgz
 
 echo "Writing in" $name
 git archive master --prefix=${name}/ --format=tgz -o dist/${name}