cmd/go: fix GOAUTH parsing for trailing slash

We were treating a url with a trailing slash differently than one
without. This CL treats them the same.

Additionally this fixes a bug in the way we iteratively try different
prefixes. We were only trying the host url but this change now tries all
different prefixes.

Fixes: #71889
Change-Id: I5d5f43000ae0e18ea8682050037253aff75ec142
Reviewed-on: https://go-review.googlesource.com/c/go/+/662435
Reviewed-by: Michael Matloob <matloob@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Sam Thanawalla <samthanawalla@google.com>

src/cmd/go/alldocs.go

@@ -2618,7 +2618,7 @@
 //		BlankLine     = '\n' .
 //
 //	Example:
-//		https://example.com/
+//		https://example.com
 //		https://example.net/api/
 //
 //		Authorization: Basic <token>

src/cmd/go/internal/auth/auth.go

@@ -142,14 +142,18 @@ func runGoAuth(client *http.Client, res *http.Response, url string) {
 // them to the request headers.
 func loadCredential(req *http.Request, url string) bool {
 	currentPrefix := strings.TrimPrefix(url, "https://")
+	currentPrefix = strings.TrimSuffix(currentPrefix, "/")
+
 	// Iteratively try prefixes, moving up the path hierarchy.
+	// E.g. example.com/foo/bar, example.com/foo, example.com
 	for {
 		headers, ok := credentialCache.Load(currentPrefix)
 		if !ok {
-			currentPrefix, _, ok = strings.Cut(currentPrefix, "/")
-			if !ok {
+			lastSlash := strings.LastIndexByte(currentPrefix, '/')
+			if lastSlash == -1 {
 				return false
 			}
+			currentPrefix = currentPrefix[:lastSlash]
 			continue
 		}
 		for key, values := range headers.(http.Header) {
@@ -166,6 +170,7 @@ func loadCredential(req *http.Request, url string) bool {
 func storeCredential(prefix string, header http.Header) {
 	// Trim "https://" prefix to match the format used in .netrc files.
 	prefix = strings.TrimPrefix(prefix, "https://")
+	prefix = strings.TrimSuffix(prefix, "/")
 	if len(header) == 0 {
 		credentialCache.Delete(prefix)
 	} else {

src/cmd/go/internal/auth/auth_test.go

@@ -71,3 +71,20 @@ func TestCredentialCacheDelete(t *testing.T) {
 		t.Errorf("loadCredential:\nhave %q\nwant %q", got.Header, want.Header)
 	}
 }
+
+func TestCredentialCacheTrailingSlash(t *testing.T) {
+	// Store a credential for api.github.com/foo/bar
+	want := http.Request{Header: make(http.Header)}
+	want.SetBasicAuth("user", "pwd")
+	storeCredential("api.github.com/foo", want.Header)
+	got := &http.Request{Header: make(http.Header)}
+	ok := loadCredential(got, "api.github.com/foo/bar")
+	if !ok || !reflect.DeepEqual(got.Header, want.Header) {
+		t.Errorf("parseNetrc:\nhave %q\nwant %q", got.Header, want.Header)
+	}
+	got2 := &http.Request{Header: make(http.Header)}
+	ok = loadCredential(got2, "https://api.github.com/foo/bar/")
+	if !ok || !reflect.DeepEqual(got2.Header, want.Header) {
+		t.Errorf("parseNetrc:\nhave %q\nwant %q", got2.Header, want.Header)
+	}
+}

src/cmd/go/internal/help/helpdoc.go

@@ -1027,7 +1027,7 @@ command
 		BlankLine     = '\n' .
 
 	Example:
-		https://example.com/
+		https://example.com
 		https://example.net/api/
 
 		Authorization: Basic <token>