Fix: next 67 savegame versions are used in PatchPacks; skip them (#8411)

Various of PatchPacks (Spring 2013, Joker, ChillPP) used versions
slightly higher than ours. Of course, as time went by, this
caught up with us, and we are now almost pushing a new version
that would conflict with them. To avoid users creating unneeded
issues about "why can I not load my savegame", lets be ahead of
the curve and flat-out refuse to load them.

Version-wise, this is totally fine. We have ~32k versions to go
before we run out (0x8000 is masked by JGRPP; we should avoid
using that). At the rate we bump savegames, this is not going to
happen in any sane reality.

3 files changed, 18 insertions, 0 deletions

diff --git a/src/lang/english.txt b/src/lang/english.txt
index 2b96f1931..7d7af8d85 100644
--- a/src/lang/english.txt
+++ b/src/lang/english.txt
@@ -4254,6 +4254,7 @@ STR_GAME_SAVELOAD_ERROR_TOO_NEW_SAVEGAME                        :Savegame is mad
 STR_GAME_SAVELOAD_ERROR_FILE_NOT_READABLE                       :File not readable
 STR_GAME_SAVELOAD_ERROR_FILE_NOT_WRITEABLE                      :File not writeable
 STR_GAME_SAVELOAD_ERROR_DATA_INTEGRITY_CHECK_FAILED             :Data integrity check failed
+STR_GAME_SAVELOAD_ERROR_PATCHPACK                               :Savegame is made with a modified version
 STR_GAME_SAVELOAD_NOT_AVAILABLE                                 :<not available>
 STR_WARNING_LOADGAME_REMOVED_TRAMS                              :{WHITE}Game was saved in version without tram support. All trams have been removed
 
diff --git a/src/saveload/saveload.cpp b/src/saveload/saveload.cpp
index 5288f9047..4f3b7e991 100644
--- a/src/saveload/saveload.cpp
+++ b/src/saveload/saveload.cpp
@@ -2689,6 +2689,7 @@ static SaveOrLoadResult DoLoad(LoadFilter *reader, bool load_check)
 
 			/* Is the version higher than the current? */
 			if (_sl_version > SAVEGAME_VERSION) SlError(STR_GAME_SAVELOAD_ERROR_TOO_NEW_SAVEGAME);
+			if (_sl_version >= SLV_START_PATCHPACKS && _sl_version <= SLV_END_PATCHPACKS) SlError(STR_GAME_SAVELOAD_ERROR_PATCHPACK);
 			break;
 		}
 
diff --git a/src/saveload/saveload.h b/src/saveload/saveload.h
index 3581a5594..7fa91a509 100644
--- a/src/saveload/saveload.h
+++ b/src/saveload/saveload.h
@@ -304,6 +304,22 @@ enum SaveLoadVersion : uint16 {
 	SLV_ENDING_YEAR,                        ///< 218  PR#7747 v1.10 Configurable ending year.
 	SLV_REMOVE_TOWN_CARGO_CACHE,            ///< 219  PR#8258 Remove town cargo acceptance and production caches.
 
+	/* Patchpacks for a while considered it a good idea to jump a few versions
+	 * above our version for their savegames. But as time continued, this gap
+	 * has been closing, up to the point we would start to reuse versions from
+	 * their patchpacks. This is not a problem from our perspective: the
+	 * savegame will simply fail to load because they all contain chunks we
+	 * cannot digest. But, this gives for ugly errors. As we have plenty of
+	 * versions anyway, we simply skip the versions we know belong to
+	 * patchpacks. This way we can present the user with a clean error
+	 * indicate he is loading a savegame from a patchpack.
+	 * For future patchpack creators: please follow a system like JGRPP, where
+	 * the version is masked with 0x8000, and the true version is stored in
+	 * its own chunk with feature toggles.
+	 */
+	SLV_START_PATCHPACKS,                   ///< 220  First known patchpack to use a version just above ours.
+	SLV_END_PATCHPACKS = 286,               ///< 286  Last known patchpack to use a version just above ours.
+
 	SL_MAX_VERSION,                         ///< Highest possible saveload version
 };