update: allow repo files to use _ in the file names

_ is a valid character for Java package names, so it should also work in
the repo file naming scheme. This makes it so it only splits the file
name based on the last _.

fdroidserver/update.py

@@ -849,12 +849,13 @@ def scan_repo_files(apkcache, repodir, knownapks, use_date_from_file=False):
             repo_file['versionName'] = shasum
             # the static ID is the SHA256 unless it is set in the metadata
             repo_file['packageName'] = shasum
-            n = name_utf8.split('_')
+
+            n = name_utf8.rsplit('_', maxsplit=1)
             if len(n) == 2:
                 packageName = n[0]
                 versionCode = n[1].split('.')[0]
                 if re.match('^-?[0-9]+$', versionCode) \
-                   and common.is_valid_package_name(name_utf8.split('_')[0]):
+                   and common.is_valid_package_name(n[0]):
                     repo_file['packageName'] = packageName
                     repo_file['versionCode'] = int(versionCode)
             srcfilename = name + b'_src.tar.gz'