internal/source: add sourcehut templates

Add source templates for the sourcehut git hosting site (git.sr.ht).

Fixes golang/go#38986.

Change-Id: I581389affe3c777828189d8aa35e3910ffe1d130
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/245039
Reviewed-by: Julie Qiu <julie@golang.org>

internal/source/source.go

@@ -449,6 +449,15 @@ var patterns = []struct {
 		regexp.MustCompile(`^(?P<repo>gitee\.com/[a-z0-9A-Z_.\-]+/[a-z0-9A-Z_.\-]+)(\.git|$)`),
 		githubURLTemplates,
 	},
+	{
+		regexp.MustCompile(`^(?P<repo>git\.sr\.ht/~[a-z0-9A-Z_.\-]+/[a-z0-9A-Z_.\-]+)`),
+		urlTemplates{
+			Directory: "{repo}/tree/{commit}/{dir}",
+			File:      "{repo}/tree/{commit}/{file}",
+			Line:      "{repo}/tree/{commit}/{file}#L{line}",
+			Raw:       "{repo}/blob/{commit}/{file}",
+		},
+	},
 	// Patterns that match the general go command pattern, where they must have
 	// a ".git" repo suffix in an import path. If matching a repo URL from a meta tag,
 	// there is no ".git".

internal/source/source_test.go

@@ -213,6 +213,26 @@ func TestModuleInfo(t *testing.T) {
 			"https://gitee.com/Billcoding/gotypes/blob/v0.1.0/type.go#L1",
 			"https://gitee.com/Billcoding/gotypes/raw/v0.1.0/type.go",
 		},
+		{
+			"sourcehut",
+			"gioui.org", "v0.0.0-20200726090130-3b95e2918359", "op/op.go",
+
+			"https://git.sr.ht/~eliasnaur/gio",
+			"https://git.sr.ht/~eliasnaur/gio/tree/3b95e2918359",
+			"https://git.sr.ht/~eliasnaur/gio/tree/3b95e2918359/op/op.go",
+			"https://git.sr.ht/~eliasnaur/gio/tree/3b95e2918359/op/op.go#L1",
+			"https://git.sr.ht/~eliasnaur/gio/blob/3b95e2918359/op/op.go",
+		},
+		{
+			"sourcehut nested",
+			"gioui.org/app", "v0.0.0-20200726090130-3b95e2918359", "app.go",
+
+			"https://git.sr.ht/~eliasnaur/gio",
+			"https://git.sr.ht/~eliasnaur/gio/tree/3b95e2918359/app",
+			"https://git.sr.ht/~eliasnaur/gio/tree/3b95e2918359/app/app.go",
+			"https://git.sr.ht/~eliasnaur/gio/tree/3b95e2918359/app/app.go#L1",
+			"https://git.sr.ht/~eliasnaur/gio/blob/3b95e2918359/app/app.go",
+		},
 		{
 			"v2 as a branch",
 			"github.com/jrick/wsrpc/v2", "v2.1.1", "rpc.go",