command: pull parallelism default up to CLI layer

/cc @knuckolls @josephholsten

command/apply.go

@@ -39,7 +39,8 @@ func (c *ApplyCommand) Run(args []string) int {
 		cmdFlags.BoolVar(&destroyForce, "force", false, "force")
 	}
 	cmdFlags.BoolVar(&refresh, "refresh", true, "refresh")
-	cmdFlags.IntVar(&c.Meta.parallelism, "parallelism", 0, "parallelism")
+	cmdFlags.IntVar(
+		&c.Meta.parallelism, "parallelism", DefaultParallelism, "parallelism")
 	cmdFlags.StringVar(&c.Meta.statePath, "state", DefaultStateFilename, "path")
 	cmdFlags.StringVar(&c.Meta.stateOutPath, "state-out", "", "path")
 	cmdFlags.StringVar(&c.Meta.backupPath, "backup", "", "path")
@@ -280,7 +281,8 @@ Options:
 
   -no-color              If specified, output won't contain any color.
 
-  -parallelism=#         Limit the number of concurrent operations.
+  -parallelism=n         Limit the number of concurrent operations.
+                         Defaults to 10.
 
   -refresh=true          Update state prior to checking for differences. This
                          has no effect if a plan file is given to apply.

command/command.go

@@ -26,6 +26,10 @@ const DefaultBackupExtension = ".backup"
 // by default.
 const DefaultDataDirectory = ".terraform"
 
+// DefaultParallelism is the limit Terraform places on total parallel
+// operations as it walks the dependency graph.
+const DefaultParallelism = 10
+
 func validateContext(ctx *terraform.Context, ui cli.Ui) bool {
 	if ws, es := ctx.Validate(); len(ws) > 0 || len(es) > 0 {
 		ui.Output(

command/plan.go

@@ -27,7 +27,8 @@ func (c *PlanCommand) Run(args []string) int {
 	cmdFlags.BoolVar(&refresh, "refresh", true, "refresh")
 	c.addModuleDepthFlag(cmdFlags, &moduleDepth)
 	cmdFlags.StringVar(&outPath, "out", "", "path")
-	cmdFlags.IntVar(&c.Meta.parallelism, "parallelism", 0, "parallelism")
+	cmdFlags.IntVar(
+		&c.Meta.parallelism, "parallelism", DefaultParallelism, "parallelism")
 	cmdFlags.StringVar(&c.Meta.statePath, "state", DefaultStateFilename, "path")
 	cmdFlags.StringVar(&c.Meta.backupPath, "backup", "", "path")
 	cmdFlags.BoolVar(&detailed, "detailed-exitcode", false, "detailed-exitcode")
@@ -185,6 +186,8 @@ Options:
   -out=path           Write a plan file to the given path. This can be used as
                       input to the "apply" command.
 
+  -parallelism=#      Limit the number of concurrent operations. Defaults to 10.
+
   -refresh=true       Update state prior to checking for differences.
 
   -state=statefile    Path to a Terraform state file to use to look