cmd/pkgsite: hide irrelevant content in local mode; add quick links

This CL contains several UI improvements when running pkgsite in local
mode via cmd/pkgsite:
- hide irrelevant or inaccurate content
- fix a bug using -gopath_mode (trim the `go env GOPATH` output)
- fix panics navigating to vuln pages
- link the GO button to the root page, rather than go.dev
- add quick-links to the homepage to browse local modules

Also:
- add -dev and -static flags, to facilitate development
- replace TestBuildGetters with more cases in TestServer
- fix some redundancy in setting the <title> element for pages;
  consolidate on using the basePage.HTMLTitle value

Updates golang/go#40371

Change-Id: I459a0d0fd39897dd4f902dd023aec653a3fb12cd
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/475755
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jamal Carvalho <jamal@golang.org>
Run-TryBot: Robert Findley <rfindley@google.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/internal/fetchdatasource/fetchdatasource.go b/internal/fetchdatasource/fetchdatasource.go
index efcd20e6..8f3e0ad0 100644
--- a/internal/fetchdatasource/fetchdatasource.go
+++ b/internal/fetchdatasource/fetchdatasource.go
@@ -379,13 +379,14 @@ func (*FetchDataSource) GetModuleReadme(ctx context.Context, modulePath, resolve
 }
 
 // SupportsSearch reports whether any of the configured Getters are searchable.
-func (ds *FetchDataSource) SupportsSearch() bool {
+func (ds *FetchDataSource) SearchSupport() internal.SearchSupport {
 	for _, g := range ds.opts.Getters {
 		if _, ok := g.(fetch.SearchableModuleGetter); ok {
-			return true
+			// Getters only support basic search.
+			return internal.BasicSearch
 		}
 	}
-	return false
+	return internal.NoSearch
 }
 
 // Search delegates search to any configured getters that support the