add more doc-comments for add_path_into_database

Author: jyn514

src/db/file.rs

@@ -142,7 +142,15 @@ pub(super) fn s3_client() -> Option<S3Client> {
     ))
 }
 
-/// Adds files into database and returns list of files with their mime type in Json
+/// Store all files in a directory and return [[mimetype, filename]] as Json
+///
+/// If there is an S3 Client configured, store files into an S3 bucket;
+/// otherwise, stores files into the 'files' table of the local database.
+///
+/// The mimetype is detected using `magic`.
+///
+/// Note that this function is used for uploading both sources
+/// and files generated by rustdoc.
 pub fn add_path_into_database<P: AsRef<Path>>(conn: &Connection,
                                               prefix: &str,
                                               path: P)