By default a run prints what it installs, the BIOS folder, the progress
at a terminal, the result and the next step. The steps, the per-file log
lines, the counts and the reasons a file is left out come back with
--verbose. --check gives the count and the folder, and lists each file
with --verbose. The installer page shows the default run and walks
through the --verbose one.
FAT, exFAT and Windows refuse < > : " | ? * in a name (fs/fat/namei_vfat.c:201-207, fs/exfat/nls.c:396-403). RetroDECK's component manifest names zxs:48.rom, zxs:if1-2.rom and snes:st018.data.rom: on an exFAT card each write failed with EINVAL on every run. The installer now probes the BIOS folder as keeps_case does, leaves those entries out and names them.
An install on Android leaves an empty .nomedia in the BIOS folder. MediaProvider hides a folder holding one and every folder below it (FileUtils.java:1587-1629, ModernMediaScanner.java:845-846, a183e2b9), and RetroArch writes none: the samples, overlays and videos of system/ showed in the gallery and music apps. --check and --dry-run write nothing.