Specialize osx-adduser script because we only use it to add one user

No need to ask people to think when setting up slaves; it introduces too much
risk of inconsistency between hosts

osx-adduser.sh

@@ -8,47 +8,27 @@
 # It's pretty simple as it uses and strings together the (rustic and ancient) commands that OSX 
 # already uses to add users.
 
-# === Typically, this is all the info you need to enter ===
+# Customized to be less interactive for Rust Buildbot slaves as of Jan 2016
 
-echo "Enter your desired user name: "
-read USERNAME
-
-echo "Enter a full name for this user: "
-read FULLNAME
-
-echo "Enter a password for this user: "
-read -s PASSWORD
-
-# ====
-
-# A list of (secondary) groups the user should belong to
-# This makes the difference between admin and non-admin users.
-
-echo "Is this an administrative user? (y/n)"
-read GROUP_ADD
+# Fail early if insufficient permissions
+if [[ $UID -ne 0 ]]; then echo "Please run $0 as root." && exit 1; fi
 
-if [ "$GROUP_ADD" = n ] ; then
-    SECONDARY_GROUPS="staff"  # for a non-admin user
-elif [ "$GROUP_ADD" = y ] ; then
-    SECONDARY_GROUPS="admin _lpadmin _appserveradm _appserverusr" # for an admin user
-else
-    echo "You did not make a valid selection!"
-fi
+USERNAME='rustbuild'
+FULLNAME='Rust Buildbot'
+# We already have admin credentials on the machine if we're running this
+# script, and access the user by su-ing to it. 
+PASSWORD=$(openssl rand -base64 30)
 
-# ====
+SECONDARY_GROUPS="admin _lpadmin _appserveradm _appserverusr" # for an admin user
 
 # Create a UID that is not currently in use
-echo "Creating an unused UID for new user..."
-
-if [[ $UID -ne 0 ]]; then echo "Please run $0 as root." && exit 1; fi
 
 # Find out the next available user ID
 MAXID=$(dscl . -list /Users UniqueID | awk '{print $2}' | sort -ug | tail -1)
 USERID=$((MAXID+1))
 
-
-# Create the user account by running dscl (normally you would have to do each of these commands one
-# by one in an obnoxious and time consuming way.
+# Create the user account by running dscl (normally you would have to do each
+# of these commands one by one in an obnoxious and time consuming way.
 echo "Creating necessary files..."
 
 dscl . -create /Users/$USERNAME
@@ -59,16 +39,13 @@ dscl . -create /Users/$USERNAME PrimaryGroupID 20
 dscl . -create /Users/$USERNAME NFSHomeDirectory /Users/$USERNAME
 dscl . -passwd /Users/$USERNAME $PASSWORD
 
-
 # Add user to any specified groups
-echo "Adding user to specified groups..."
 
 for GROUP in $SECONDARY_GROUPS ; do
     dseditgroup -o edit -t user -a $USERNAME $GROUP
 done
 
 # Create the home directory
-echo "Creating home directory..."
 createhomedir -c 2>&1 | grep -v "shell-init"
 
 echo "Created user #$USERID: $USERNAME ($FULLNAME)"