fix(desktop): Keep an installed app when its update lookup fails
An update reads the registry's layer digest before removing anything,
but a lookup that failed came back as an empty digest, which never
matches the installed one: the update removed the app, and the download
that followed failed on the same empty digest, leaving nothing. A
registry outage did this to every app it touched, and an image dropping
this architecture did it through get_blob_sha calling cleanup, which
only dl_layer defines. get_blob_sha now returns 1 where no manifest is
for this architecture, as dl_layer already reads its status, and update
exits 1 with the installed copy left as it is when the lookup fails or
comes back empty.
- Reproduced: on 012b80c,
proot-apps update fooagainst a stub
registry serving an index without this architecture, and against one
failing every request, prints "Removing app root", exits 1, and leaves
the app folder gone. - Fixed: both now exit 1 naming the failure, with the folder intact.
- Behavior: an update to a new digest removes and reinstalls as before;
getof an image without this architecture still prints "No manifest
available ... cannot fetch", exits 1, and leaves nothing; the local
repository comparison (install, list, completion, run, update,
uninstall, remove) prints the same output as before the change; the
shell suite passes 170/170.