command/format: Show resource diff with header "comment"

This extra comment line gives us a place to show the full resource address
(since the block header line only includes type and name) and also allows
us to explain in long form the meaning of the change icon on the following
line.

command/format/diff.go

@@ -14,6 +14,7 @@ import (
 	"github.com/hashicorp/terraform/configs/configschema"
 	"github.com/hashicorp/terraform/plans"
 	"github.com/hashicorp/terraform/plans/objchange"
+	"github.com/hashicorp/terraform/states"
 )
 
 // ResourceChange returns a string representation of a change to a particular
@@ -41,7 +42,27 @@ func ResourceChange(
 		}
 	}
 
-	buf.WriteString(color.Color("[reset]"))
+	dispAddr := addr.String()
+	if change.DeposedKey != states.NotDeposed {
+		dispAddr = fmt.Sprintf("%s (deposed object %s)", dispAddr, change.DeposedKey)
+	}
+
+	switch change.Action {
+	case plans.Create:
+		buf.WriteString(color.Color(fmt.Sprintf("[bold]  # %s[reset] will be created", dispAddr)))
+	case plans.Read:
+		buf.WriteString(color.Color(fmt.Sprintf("[bold]  # %s[reset] will be read during apply\n  # (config refers to values not yet known)", dispAddr)))
+	case plans.Update:
+		buf.WriteString(color.Color(fmt.Sprintf("[bold]  # %s[reset] will be updated in-place", dispAddr)))
+	case plans.Replace:
+		buf.WriteString(color.Color(fmt.Sprintf("[bold]  # %s[reset] must be [bold][red]replaced", dispAddr)))
+	case plans.Delete:
+		buf.WriteString(color.Color(fmt.Sprintf("[bold]  # %s[reset] will be [bold][red]destroyed", dispAddr)))
+	default:
+		// should never happen, since the above is exhaustive
+		buf.WriteString(fmt.Sprintf("%s has an action the plan renderer doesn't support (this is a bug)", dispAddr))
+	}
+	buf.WriteString(color.Color("[reset]\n"))
 
 	switch change.Action {
 	case plans.Create:
@@ -55,39 +76,28 @@ func ResourceChange(
 	case plans.Delete:
 		buf.WriteString(color.Color("[red]  -[reset] "))
 	default:
-		// should never happen, since the above is exhaustive
 		buf.WriteString(color.Color("??? "))
 	}
 
 	switch addr.Resource.Resource.Mode {
 	case addrs.ManagedResourceMode:
-		buf.WriteString(color.Color(fmt.Sprintf(
+		buf.WriteString(fmt.Sprintf(
-			"resource [bold]%q[reset] [bold]%q[reset]",
+			"resource %q %q",
 			addr.Resource.Resource.Type,
 			addr.Resource.Resource.Name,
-		)))
+		))
-		if addr.Resource.Key != addrs.NoKey {
-			buf.WriteString(fmt.Sprintf(" %s", addr.Resource.Key))
-		}
 	case addrs.DataResourceMode:
-		buf.WriteString(color.Color(fmt.Sprintf(
+		buf.WriteString(fmt.Sprintf(
-			"data [bold]%q[reset] [bold]%q[reset] ",
+			"data %q %q ",
 			addr.Resource.Resource.Type,
 			addr.Resource.Resource.Name,
-		)))
+		))
-		if addr.Resource.Key != addrs.NoKey {
-			buf.WriteString(fmt.Sprintf(" %s", addr.Resource.Key))
-		}
 	default:
 		// should never happen, since the above is exhaustive
 		buf.WriteString(addr.String())
 	}
 
-	buf.WriteString(" {")
+	buf.WriteString(" {\n")
-	if change.Action == plans.Replace {
-		buf.WriteString(color.Color(" [bold][red]# new resource required[reset]"))
-	}
-	buf.WriteString("\n")
 
 	p := blockBodyDiffPrinter{
 		buf:             &buf,
@@ -128,7 +138,7 @@ type blockBodyDiffPrinter struct {
 	requiredReplace cty.PathSet
 }
 
-const forcesNewResourceCaption = " [red]# (forces new resource)[reset]"
+const forcesNewResourceCaption = " [red]# forces replacement[reset]"
 
 func (p *blockBodyDiffPrinter) writeBlockBodyDiff(schema *configschema.Block, old, new cty.Value, indent int, path cty.Path) {
 	path = ctyEnsurePathCapacity(path, 1)