fix(builder): SteamCMD is the only option for Linux Steam servers; settings must reach the server

cmd/gbrgames/research.go

@@ -174,9 +174,10 @@ const researchPrompt = "You research how to host a game's dedicated server for G
 	"the ways this game's dedicated server can be run (variants): separate editions of the game with their own server, " +
 	"crossplay builds, or notably different server images. For each variant give:\n" +
 	"- images: how to run this server, best first. When the game has a dedicated server on Steam that runs on Linux, " +
-	"cm2network/steamcmd (the plain SteamCMD route, installing the server into /server) always comes first and that " +
-	"variant is the recommended one. Then Docker Hub images that appear in the pages and run as a non-root user " +
-	"(needed for servers that only exist for Windows).\n" +
+	"cm2network/steamcmd (the plain SteamCMD route, installing the server into /server) is its only image, and " +
+	"there is no separate variant for a community image of the same server: those keep their saves outside /server. " +
+	"Docker Hub images that appear in the pages and run as a non-root user are only for servers that aren't on Steam " +
+	"for Linux (Windows-only servers that need Proton or Wine, games not on Steam).\n" +
 	"- steamAppId: the Steam app id of the DEDICATED SERVER (not the game itself), if installed via SteamCMD; else \"\".\n" +
 	"- startupHint: the command that starts the server from its install folder /server, with the launch options " +
 	"for name, port, world and save location exactly as the pages document them; \"\" if unknown.\n" +
@@ -311,7 +312,7 @@ func verifyVariants(res *researchResult) {
 		}
 	}
 	apps := steamApps(appIDs)
-	anyRunnable := false
+	anyRunnable, linuxSteam := false, false
 	for i := range res.Variants {
 		v := &res.Variants[i]
 		var images []string
@@ -333,7 +334,8 @@ func verifyVariants(res *researchResult) {
 				v.Verified = append(v.Verified, fmt.Sprintf("Steam app %s is %q", v.SteamAppID, app.name))
 				v.Images = withSteamCMD(v.Images, app.linux)
 				if app.linux {
-					v.Verified = append(v.Verified, "it ships a Linux server, so the SteamCMD option (installing it into /server) is recommended")
+					linuxSteam = true
+					v.Verified = append(v.Verified, "it ships a Linux server, so it is installed with SteamCMD into /server")
 				}
 			} else {
 				v.Problems = append(v.Problems, "Steam app "+v.SteamAppID+" not found for anonymous SteamCMD")
@@ -352,10 +354,26 @@ func verifyVariants(res *researchResult) {
 		res.Reason = "unknown"
 		res.Message = "No variant has a Docker image or Steam app that could be confirmed. " + res.Message
 	}
+	if linuxSteam {
+		res.Variants = steamCMDOnly(res.Variants)
+	}
 	res.Variants = oneOptionPerImage(res.Variants)
 	recommend(res.Variants)
 }
 
+// steamCMDOnly keeps only the SteamCMD options once the game has a Linux server on Steam. Ready-made images
+// of such servers keep their files and saves in their own folders (/config, /home/...), outside /server,
+// and read settings from their own variables, so they can't be made or repaired into a working template.
+func steamCMDOnly(variants []variant) []variant {
+	var out []variant
+	for _, v := range variants {
+		if len(v.Images) > 0 && isSteamCMDImage(v.Images[0]) && v.SteamAppID != "" {
+			out = append(out, v)
+		}
+	}
+	return out
+}
+
 // recommend marks exactly one variant recommended, among the runnable ones. A variant that installs a Linux
 // server with SteamCMD comes before the model's choice: it keeps everything under /server, as nodes need.
 func recommend(variants []variant) {
@@ -422,7 +440,7 @@ func steamApps(apps []string) map[string]steamApp {
 }
 
 // withSteamCMD adds the plain SteamCMD route to a variant's images. When the Steam app ships a Linux server
-// it goes first: it installs into /server, which nodes keep, while ready-made images often keep their
+// it is the only route: it installs into /server, which nodes keep, while ready-made images keep their
 // files elsewhere. For Windows-only servers it stays last, behind images that bring Proton or Wine.
 func withSteamCMD(images []string, linux bool) []string {
 	var others []string
@@ -432,7 +450,7 @@ func withSteamCMD(images []string, linux bool) []string {
 		}
 	}
 	if linux {
-		return append([]string{"cm2network/steamcmd"}, others...)
+		return []string{"cm2network/steamcmd"}
 	}
 	return append(others, "cm2network/steamcmd")
 }