screen: Drop pid prefixes from session name completions where possible.

Thanks-to: Alexey Zaytsev <alexey.zaytsev@gmail.com>

completions/screen

@@ -4,9 +4,23 @@ have screen || return
 
 _screen_sessions()
 {
-    COMPREPLY=( $( compgen -W "$( command screen -ls | sed -ne \
+    local sessions=( $( command screen -ls | sed -ne \
-        's|^\t\{1,\}\([0-9]\{1,\}\.[^\t]\{1,\}\).*'"$1"'.*$|\1|p' )" \
+        's|^\t\{1,\}\([0-9]\{1,\}\.[^\t]\{1,\}\).*'"$1"'.*$|\1|p' ) )
-        -- "$cur" ) )
+    if [[ $cur == +([0-9])?(.*) ]]; then
+        # Complete sessions including pid prefixes
+        COMPREPLY=( $( compgen -W '${sessions[@]}' -- "$cur" ) )
+    else
+        # Create unique completions, dropping pids where possible
+        local -A res
+        local i tmp
+        for i in ${sessions[@]}; do
+            res[${i/#+([0-9])./}]+=" $i"
+        done
+        for i in ${!res[@]}; do
+            [[ ${res[$i]} == \ *\ * ]] && tmp+=" ${res[$i]}" || tmp+=" $i"
+        done
+        COMPREPLY=( $( compgen -W '$tmp' -- "$cur" ) )
+    fi
 } &&
 _screen()
 {