cmd/gorelease: remove empty summaries for comparisons

gorelease should not print an empty "# summary" section. Previously,
this happened when comparing modules with different paths. In this
case, the user probably just wants to compare APIs, and gorelease
shouldn't make a judgement about whether versions are valid.

For golang/go#46372

Change-Id: I1bbd032c943ba9f14c1a001fd3112d7c6eb3a635
Reviewed-on: https://go-review.googlesource.com/c/exp/+/333370
Trust: Jay Conrod <jayconrod@google.com>
Trust: Jean de Klerk <deklerk@google.com>
Run-TryBot: Jay Conrod <jayconrod@google.com>
Reviewed-by: Jean de Klerk <deklerk@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
diff --git a/cmd/gorelease/report.go b/cmd/gorelease/report.go
index fa5d581..3895c98 100644
--- a/cmd/gorelease/report.go
+++ b/cmd/gorelease/report.go
@@ -61,6 +61,10 @@
 		buf.WriteString(p.String())
 	}
 
+	if !r.canVerifyReleaseVersion() {
+		return buf.String()
+	}
+
 	if len(r.release.diagnostics) > 0 {
 		buf.WriteString("# diagnostics\n")
 		for _, d := range r.release.diagnostics {
@@ -88,7 +92,7 @@
 		} else {
 			fmt.Fprintf(buf, "Suggested version: %[1]s (with tag %[2]s%[1]s)\n", r.release.version, r.release.tagPrefix)
 		}
-	} else if r.release.version != "" && r.canVerifyReleaseVersion() {
+	} else if r.release.version != "" {
 		if r.release.tagPrefix == "" {
 			fmt.Fprintf(buf, "%s is a valid semantic version for this release.\n", r.release.version)
 
diff --git a/cmd/gorelease/testdata/basic/v1_fork_base_modpath_version_verify.test b/cmd/gorelease/testdata/basic/v1_fork_base_modpath_version_verify.test
index 80ba542..a662cb1 100644
--- a/cmd/gorelease/testdata/basic/v1_fork_base_modpath_version_verify.test
+++ b/cmd/gorelease/testdata/basic/v1_fork_base_modpath_version_verify.test
@@ -9,5 +9,3 @@
 A2: removed
 ## compatible changes
 A3: added
-
-# summary
diff --git a/cmd/gorelease/testdata/basic/v1_fork_base_verify.test b/cmd/gorelease/testdata/basic/v1_fork_base_verify.test
index 650fff4..ff3faab 100644
--- a/cmd/gorelease/testdata/basic/v1_fork_base_verify.test
+++ b/cmd/gorelease/testdata/basic/v1_fork_base_verify.test
@@ -13,5 +13,3 @@
 # example.com/basicfork/b
 ## incompatible changes
 package removed
-
-# summary
diff --git a/cmd/gorelease/testdata/internalcompat/internalcompat.test b/cmd/gorelease/testdata/internalcompat/internalcompat.test
index 9436bee..9bf59a3 100644
--- a/cmd/gorelease/testdata/internalcompat/internalcompat.test
+++ b/cmd/gorelease/testdata/internalcompat/internalcompat.test
@@ -3,4 +3,3 @@
 release=v1.0.1
 base=example.com/internalcompat/a@v1.0.0
 -- want --
-# summary