redis-trib: allow to reshard in non-interactive way.

The introduction of --from --to --slots --yes options allow to reshard
from cli in an automated way from scripts. The code is ugly and needs
refactoring as soon as we get it in RC / stable release.

src/redis-trib.rb

@@ -821,11 +821,26 @@ class RedisTrib
             puts "*** Please fix your cluster problems before resharding"
             exit 1
         end
+
+        # Get number of slots
+        if opt['slots']
+            numslots = opt['slots'].to_i
+        else
             numslots = 0
             while numslots <= 0 or numslots > ClusterHashSlots
                 print "How many slots do you want to move (from 1 to #{ClusterHashSlots})? "
                 numslots = STDIN.gets.to_i
             end
+        end
+
+        # Get the target instance
+        if opt['to']
+            target = get_node_by_name(opt['to'])
+            if !target || target.has_flag?("slave")
+                xputs "*** The specified node is not known or not a master, please retry."
+                exit 1
+            end
+        else
             target = nil
             while not target
                 print "What is the receiving node ID? "
@@ -835,7 +850,20 @@ class RedisTrib
                     target = nil
                 end
             end
+        end
+
+        # Get the source instances
         sources = []
+        if opt['from']
+            opt['from'].split(',').each{|node_id|
+                src = get_node_by_name(node_id)
+                if !src || src.has_flag?("slave")
+                    xputs "*** The specified node is not known or is not a master, please retry."
+                    exit 1
+                end
+                sources << src
+            }
+        else
             xputs "Please enter all the source node IDs."
             xputs "  Type 'all' to use all the nodes as source nodes for the hash slots."
             xputs "  Type 'done' once you entered all the source nodes IDs."
@@ -844,18 +872,9 @@ class RedisTrib
                 line = STDIN.gets.chop
                 src = get_node_by_name(line)
                 if line == "done"
-                if sources.length == 0
-                    puts "No source nodes given, operation aborted"
-                    exit 1
-                else
                     break
-                end
                 elsif line == "all"
-                @nodes.each{|n|
+                    sources = "all"
-                    next if n.info[:name] == target.info[:name]
-                    next if n.has_flag?("slave")
-                    sources << n
-                }
                     break
                 elsif !src || src.has_flag?("slave")
                     xputs "*** The specified node is not known or is not a master, please retry."
@@ -865,6 +884,29 @@ class RedisTrib
                     sources << src
                 end
             end
+        end
+
+        if sources.length == 0
+            puts "*** No source nodes given, operation aborted"
+            exit 1
+        end
+
+        # Handle soures == all.
+        if sources == "all"
+            sources = []
+            @nodes.each{|n|
+                next if n.info[:name] == target.info[:name]
+                next if n.has_flag?("slave")
+                sources << n
+            }
+        end
+
+        # Check if the destination node is the same of any source nodes.
+        if sources.index(target)
+            xputs "*** Target node is also listed among the source nodes!"
+            exit 1
+        end
+
         puts "\nReady to move #{numslots} slots."
         puts "  Source nodes:"
         sources.each{|s| puts "    "+s.info_string}
@@ -873,9 +915,11 @@ class RedisTrib
         reshard_table = compute_reshard_table(sources,numslots)
         puts "  Resharding plan:"
         show_reshard_table(reshard_table)
+        if !opt['yes']
             print "Do you want to proceed with the proposed reshard plan (yes/no)? "
             yesno = STDIN.gets.chop
             exit(1) if (yesno != "yes")
+        end
         reshard_table.each{|e|
             move_slot(e[:source],target,e[:slot],:verbose=>true)
         }
@@ -1253,7 +1297,8 @@ COMMANDS={
 ALLOWED_OPTIONS={
     "create" => {"replicas" => true},
     "add-node" => {"slave" => false, "master-id" => true},
-    "import" => {"from" => :required}
+    "import" => {"from" => :required},
+    "reshard" => {"from" => true, "to" => true, "slots" => true, "yes" => false}
 }
 
 def show_help