chore: improve error message around gitaskpass failures (#9407)

cli/gitaskpass.go

@@ -44,7 +44,13 @@ func (r *RootCmd) gitAskpass() *clibase.Cmd {
 				if errors.As(err, &apiError) && apiError.StatusCode() == http.StatusNotFound {
 					// This prevents the "Run 'coder --help' for usage"
 					// message from occurring.
-					cliui.Errorf(inv.Stderr, "%s\n", apiError.Message)
+					lines := []string{apiError.Message}
+					if apiError.Detail != "" {
+						lines = append(lines, apiError.Detail)
+					}
+					cliui.Warn(inv.Stderr, "Coder was unable to handle this git request. The default git behavior will be used instead.",
+						lines...,
+					)
 					return cliui.Canceled
 				}
 				return xerrors.Errorf("get git token: %w", err)