golink: allow -resolve-from-backup to resolve alias links

It's not uncommon to have multiple links pointing to the same
destination, for example to handle different spellings of a word or
because different people created them at different times.

A common best practice is to select one as the "primary" link and point
the others to that link as "aliases".  This change updates resolveLink
to follow those aliases so that the final destination is returned when
using `golink -resolve-from-backup`.

Signed-off-by: Will Norris <[email protected]>

Author: willnorris

golink.go

@@ -667,5 +667,11 @@ func resolveLink(link string) (string, error) {
 	if err != nil {
 		return "", err
 	}
-	return expandLink(l.Long, expandEnv{Now: time.Now().UTC(), Path: remainder})
+	dst, err := expandLink(l.Long, expandEnv{Now: time.Now().UTC(), Path: remainder})
+	if err == nil {
+		if u, uErr := url.Parse(dst); uErr == nil && (u.Hostname() == "" || u.Hostname() == *hostname) {
+			dst, err = resolveLink(dst)
+		}
+	}
+	return dst, err
 }

golink_test.go

@@ -103,6 +103,8 @@ func TestResolveLink(t *testing.T) {
 	}
 	db.Save(&Link{Short: "meet", Long: "https://meet.google.com/lookup/"})
 	db.Save(&Link{Short: "cs", Long: "http://codesearch/{{with .Path}}search?q={{.}}{{end}}"})
+	db.Save(&Link{Short: "m", Long: "http://go/meet"})
+	db.Save(&Link{Short: "chat", Long: "/meet"})
 
 	tests := []struct {
 		link string
@@ -137,6 +139,16 @@ func TestResolveLink(t *testing.T) {
 			link: "cs/term",
 			want: "http://codesearch/search?q=term",
 		},
+		{
+			// aliased go links with hostname
+			link: "m/foo",
+			want: "https://meet.google.com/lookup/foo",
+		},
+		{
+			// aliased go links without hostname
+			link: "chat/foo",
+			want: "https://meet.google.com/lookup/foo",
+		},
 	}
 	for _, tt := range tests {
 		name := "golink " + tt.link