cmgerrit: if command line input is null, prompt user for the variables

cmgerrit: cleanup wording to make it easier to understand
diff --git a/tools/cmgerrit b/tools/cmgerrit
index 6a5c24d..bc79d5a 100755
--- a/tools/cmgerrit
+++ b/tools/cmgerrit
@@ -2,7 +2,26 @@
 #
 # Gerrit tool for easiness of submitting changes to CM repos
 # Wes Garner
-# Usage: cmgerrit <Gerrit Username> <Repo> <for/changes> <Branch>
+# Usage: cmgerrit <CM Gerrit username> <repo> <for/changes> <branch/change-id>
+# Note: for = new submissions, changes = new patch set for current submission
 #
 
-git push ssh://$1@review.cyanogenmod.com:29418/CyanogenMod/$2 HEAD:refs/$3/$4
+user=$1
+repo=$2
+mode=$3
+target=$4
+
+if [ -z $user ]
+then
+	echo "Type your CyanogenMod Gerrit username: "
+	read user
+	echo "What is the repository you are submitting to? (ex. android_vendor_cyanogen) "
+	read repo
+	echo "Is this a new change or a new patchset to a current change? (for = new, changes = patch set) "
+	read mode
+	echo "What is the branch (for a new change) OR change-id (for a current change) you are working with? "
+	read target
+fi
+
+git push ssh://$user@review.cyanogenmod.com:29418/CyanogenMod/$repo HEAD:refs/$mode/$target
+