relnote: use code elements for package headings

The headings for the "minor changes" section are package names,
so render them as code elements.

For golang/go#64169.

Change-Id: Ib2864dd295b11e7a32b7903e06dd6bf721915caf
Reviewed-on: https://go-review.googlesource.com/c/build/+/577300
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

relnote/relnote.go

@@ -204,7 +204,7 @@ func stdlibPackageHeading(pkg string, lastLine int) *md.Heading {
 			Position: pos,
 			Inline: []md.Inline{
 				&md.Link{
-					Inner: []md.Inline{&md.Plain{Text: pkg}},
+					Inner: []md.Inline{&md.Code{Text: pkg}},
 					URL:   "/pkg/" + pkg + "/",
 				},
 			},

relnote/relnote_test.go

@@ -115,9 +115,7 @@ func TestStdlibPackage(t *testing.T) {
 func TestStdlibPackageHeading(t *testing.T) {
 	h := stdlibPackageHeading("net/http", 1)
 	got := md.ToMarkdown(h)
-	want := "#### [net/http](/pkg/net/http/)\n"
-	// TODO(jba): use a code element for the heading; the following is the correct value of "want":
-	// want := "#### [`net/http`](/pkg/net/http/)\n"
+	want := "#### [`net/http`](/pkg/net/http/)\n"
 	if got != want {
 		t.Errorf("\ngot  %q\nwant %q", got, want)
 	}

relnote/testdata/merge/go121.txt

@@ -347,7 +347,7 @@ made with the Go 1 [promise of compatibility](/doc/go1compat)
 in mind.
 There are also various performance improvements, not enumerated here.
 
-#### [archive/tar](/pkg/archive/tar/)
+#### [`archive/tar`](/pkg/archive/tar/)
 
 <!-- https://go.dev/issue/54451, CL 491175 -->
 The implementation of the
@@ -357,7 +357,7 @@ interface returned by
 now implements a `String` method that calls
 [`io/fs.FormatFileInfo`](/pkg/io/fs/#FormatFileInfo).
 
-#### [archive/zip](/pkg/archive/zip/)
+#### [`archive/zip`](/pkg/archive/zip/)
 
 <!-- https://go.dev/issue/54451, CL 491175 -->
 The implementation of the
@@ -367,7 +367,7 @@ interface returned by
 now implements a `String` method that calls
 [`io/fs.FormatFileInfo`](/pkg/io/fs/#FormatFileInfo).
 
-#### [bytes](/pkg/bytes/)
+#### [`bytes`](/pkg/bytes/)
 
 <!-- https://go.dev/issue/53685, CL 474635 -->
 The [`Buffer`](/pkg/bytes/#Buffer) type
@@ -379,7 +379,7 @@ These may be used along with the
 method to append directly to the `Buffer`.
 ways different.
 
-#### [debug/elf](/pkg/debug/elf/)
+#### [`debug/elf`](/pkg/debug/elf/)
 
 <!-- https://go.dev/issue/56887, CL 452496 -->
 The constant flags permitted in a `DT_FLAGS_1`
@@ -401,14 +401,14 @@ given dynamic tag.
 The package now defines the constant
 [`R_PPC64_REL24_P9NOTOC`](/pkg/debug/elf/#R_PPC64_REL24_P9NOTOC).
 
-#### [net](/pkg/net/)
+#### [`net`](/pkg/net/)
 
 <!-- https://go.dev/issue/59166, https://go.dev/issue/56539 -->
 <!-- CL 471136, CL 471137, CL 471140 -->
 On Linux, the [net](/pkg/net/) package can now use
 Multipath TCP when the kernel supports it.
 
-#### [net/http](/pkg/net/http/)
+#### [`net/http`](/pkg/net/http/)
 
 <!-- CL 472636 -->
 The new [`ResponseController.EnableFullDuplex`](/pkg/net/http#ResponseController.EnableFullDuplex)

relnote/testdata/merge/symbol_links.txt

@@ -12,7 +12,7 @@ like [`bytes.Buffer`](/pkg/bytes#Buffer)
 and [`bytes.Reader.Read`](/pkg/bytes#Reader.Read).
 This: s[math] is not a link.
 
-#### [bytes](/pkg/bytes/)
+#### [`bytes`](/pkg/bytes/)
 
 Inside this file, [`Buffer`](/pkg/bytes#Buffer) can be used instead of
 [`bytes.Buffer`](/pkg/bytes#Buffer).