update config documentation (#361)

README.md

@@ -144,18 +144,12 @@ game folder.
 
 Basic fields:
 
-field | purpose
------ | -------
-`DeveloperMode` | Default `false` (except in _SMAPI for developers_ releases). Whether to enable features intended for mod developers (mainly more detailed console logging).
+field             | purpose
+----------------- | -------
+`DeveloperMode`   | Default `false` (except in _SMAPI for developers_ releases). Whether to enable features intended for mod developers (mainly more detailed console logging).
 `CheckForUpdates` | Default `true`. Whether SMAPI should check for a newer version when you load the game. If a new version is available, a small message will appear in the console. This doesn't affect the load time even if your connection is offline or slow, because it happens in the background.
-`VerboseLogging` | Default `false`. Whether SMAPI should log more information about the game context.
-
-Advanced fields (changing these isn't recommended and may destabilise your game):
-
-field | purpose
------ | -------
-`DisabledMods` | A list of mods to consider obsolete and not load.
-`ModCompatibility` | A list of mod versions SMAPI should consider compatible or broken regardless of whether it detects incompatible code. This can be used to force SMAPI to load an incompatible mod, though that isn't recommended.
+`VerboseLogging`  | Default `false`. Whether SMAPI should log more information about the game context.
+`ModData`         | Internal metadata about SMAPI mods. Changing this isn't recommended and may destabilise your game. See documentation in the file.
 
 ### Command-line arguments
 The SMAPI installer recognises three command-line arguments:

src/StardewModdingAPI/StardewModdingAPI.config.json

@@ -39,10 +39,30 @@ This file contains advanced configuration for SMAPI. You generally shouldn't cha
   "VerboseLogging": false,
 
   /**
-   * A list of mod versions SMAPI should consider compatible or broken regardless of whether it
-   * detects incompatible code. The default for each record is to assume broken; to force SMAPI to
-   * load a mod regardless of compatibility checks, add a "Compatibility": "AssumeCompatible" field.
-   * Changing this field is not recommended and may destabilise your game.
+   * Extra metadata about some SMAPI mods. All fields except 'ID' are optional.
+   *
+   * - 'ID' uniquely identifies the mod across all versions, even if its manifest fields changed or
+   *   the mod doesn't have a unique ID. The format is as follows:
+   *      - If the mod's identifier changed over time, multiple variants are separated by |.
+   *      - Each variant can take one of two forms: a simple string matching the mod's UniqueID,
+   *        or a JSON structure containing any of three manifest fields (ID, Name, and Author) to
+   *        match.
+   *
+   * - 'Defaults' specifies fields to inject into the mod's manifest if they're not already set.
+   *   Supported fields: ChucklefishID, GitHubProject, and NexusID.
+   *
+   * - 'AlternativeUrl' specifies a URL where the player can find an unofficial update or
+   *   alternative if the mod is no longer compatible.
+   *
+   * - 'Compatibility' overrides SMAPI's normal compatibility detection. The keys are version
+   *   ranges in the form lower~upper, where either side can be blank for an unbounded range. (For
+   *   example, "~1.0" means all versions up to 1.0 inclusively.) The values have two fields:
+   *      - 'Status' specifies the compatibility. Valid values are Obsolete (SMAPI won't load it
+   *        because the mod should no longer be used), AssumeBroken (SMAPI won't load it because
+   *        the specified version isn't compatible), or AssumeCompatible (SMAPI will load it even
+   *        if it detects incompatible code).
+   *      - 'ReasonPhrase' (optional) specifies a message to show to the player explaining why the
+   *        mod isn't loaded. This has no effect for AssumeCompatible.
    */
   "ModData": [
     {