Updates: Allow downgrades (#1051)

ExplorerPatcher/settings.reg

@@ -562,6 +562,8 @@
 "UpdatePolicy"=dword:00000001
 ;b Receive pre-release versions, if available (not recommended)
 "UpdatePreferStaging"=dword:00000000
+;b Suggest the latest version on the server, even if it's older (not recommended)
+"UpdateAllowDowngrades"=dword:00000000
 ;t Update servers:
 ;w Releases
 ;Type a URL that serves resources adhering to GitHub's releases API. To learn how to configure your own update server, please consult the wiki.

ExplorerPatcher/settings10.reg

@@ -492,6 +492,8 @@
 "UpdatePolicy"=dword:00000001
 ;b Receive pre-release versions, if available (not recommended)
 "UpdatePreferStaging"=dword:00000000
+;b Suggest the latest version on the server, even if it's older (not recommended)
+"UpdateAllowDowngrades"=dword:00000000
 ;t Update servers:
 ;w Releases
 ;Type a URL that serves resources adhering to GitHub's releases API. To learn how to configure your own update server, please consult the wiki.

ExplorerPatcher/updates.c

@@ -287,7 +287,9 @@ BOOL IsUpdateAvailableHelper(
                                                         }
                                                     }
                                                 }
-                                                if (res == -1)
+                                                DWORD dwAllowDowngrades = FALSE, dwSize = sizeof(DWORD);
+                                                RegGetValueW(HKEY_CURRENT_USER, _T(REGPATH), L"UpdateAllowDowngrades", RRF_RT_DWORD, NULL, &dwAllowDowngrades, &dwSize);
+                                                if ((res == 1 && dwAllowDowngrades) || res == -1)
                                                 {
                                                     bIsUpdateAvailable = TRUE;
                                                 }