custom adapters doc file (incomplete)

doc/Custom adapters.md

@@ -0,0 +1,9 @@
+## Custom adapters
+
+Since [version], you can specify custom adapters that invoke external preprocessing scripts in the config file.
+
+[Todo: how]
+
+[Todo: why not just use --pre yourself (copy/see https://github.com/phiresky/ripgrep-all/issues/60)]
+
+If you think your adapter config is useful, you can share it by opening an issue with the title: "Custom adapter: xyz"

src/preproc_cache.rs

@@ -94,7 +94,10 @@ impl PreprocCache for LmdbCache {
 
         match cached {
             Some(rkv::Value::Blob(cached)) => {
-                debug!("cache HIT, reading from cache");
+                debug!(
+                    "cache HIT, reading {} (compressed) from cache",
+                    print_bytes(cached.len() as f64)
+                );
                 debug!("reading from cache took {}", print_dur(start));
                 callback(cached)?;
             }