Ignore some functions in the Go template when header is rendered

This fix ignore some functions in the Go template when header is
redendered, so that `--format "{{truncate .ID 1}}"` will still
be able to redener the header correctly.

Additional test cases have been added to the unit test.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

command/formatter/container_test.go

@@ -226,6 +226,14 @@ size: 0B
 			Context{Format: NewContainerFormat("{{.Image}}", false, true)},
 			"ubuntu\nubuntu\n",
 		},
+		// Special headers for customerized table format
+		{
+			Context{Format: NewContainerFormat(`table {{truncate .ID 5}}\t{{json .Image}} {{.RunningFor}}/{{title .Status}}/{{pad .Ports 2 2}}.{{upper .Names}} {{lower .Status}}`, false, true)},
+			`CONTAINER ID        IMAGE CREATED/STATUS/  PORTS  .NAMES STATUS
+conta               "ubuntu" 24 hours ago//.FOOBAR_BAZ 
+conta               "ubuntu" 24 hours ago//.FOOBAR_BAR 
+`,
+		},
 	}
 
 	for _, testcase := range cases {

command/formatter/disk_usage_test.go

@@ -2,13 +2,8 @@ package formatter
 
 import (
 	"bytes"
-	//"encoding/json"
-	//"strings"
 	"testing"
-	//"time"
 
-	//"github.com/docker/docker/api/types"
-	//"github.com/docker/docker/pkg/stringid"
 	"github.com/docker/docker/pkg/testutil/assert"
 )
 
@@ -44,10 +39,6 @@ VOLUME NAME         LINKS               SIZE
 	}
 
 	for _, testcase := range cases {
-		//networks := []types.NetworkResource{
-		//	{ID: "networkID1", Name: "foobar_baz", Driver: "foo", Scope: "local", Created: timestamp1},
-		//	{ID: "networkID2", Name: "foobar_bar", Driver: "bar", Scope: "local", Created: timestamp2},
-		//}
 		out := bytes.NewBufferString("")
 		testcase.context.Output = out
 		testcase.context.Write()

command/formatter/formatter.go

@@ -73,7 +73,7 @@ func (c *Context) postFormat(tmpl *template.Template, subContext subContext) {
 	if c.Format.IsTable() {
 		t := tabwriter.NewWriter(c.Output, 20, 1, 3, ' ', 0)
 		buffer := bytes.NewBufferString("")
-		tmpl.Execute(buffer, subContext.FullHeader())
+		tmpl.Funcs(templates.HeaderFunctions).Execute(buffer, subContext.FullHeader())
 		buffer.WriteTo(t)
 		t.Write([]byte("\n"))
 		c.buffer.WriteTo(t)

command/formatter/image.go

@@ -76,20 +76,6 @@ func ImageWrite(ctx ImageContext, images []types.ImageSummary) error {
 	render := func(format func(subContext subContext) error) error {
 		return imageFormat(ctx, images, format)
 	}
-	imageCtx := imageContext{}
-	imageCtx.header = map[string]string{
-		"ID":           imageIDHeader,
-		"Repository":   repositoryHeader,
-		"Tag":          tagHeader,
-		"Digest":       digestHeader,
-		"CreatedSince": createdSinceHeader,
-		"CreatedAt":    createdAtHeader,
-		"Size":         sizeHeader,
-		"Containers":   containersHeader,
-		"VirtualSize":  sizeHeader,
-		"SharedSize":   sharedSizeHeader,
-		"UniqueSize":   uniqueSizeHeader,
-	}
 	return ctx.Write(newImageContext(), render)
 }