Ubuntu has started depreciating the Debian installer in focal
and moved the installer images to a different path. In versions
after focal, they are completly removed. This basically gives
us more time to figure out how to use the new system.
the logic here was wrong.
if we managed to find the link target (the physical index file) pointed to
by our old symlink we want to remove it (this is basically "cleaning up old
index" logic).
previously we'd try to only delete it when the ReadLink came back with
error. which had two serious issues with it:
a) linkTarget was empty, so we basically called Remove("") which would
delete the storage -> root <- directory if the root is a symlink!
b) we'd leak old indexes as the cleanup logic only ran if there was en
error which would ordinarily never be
new code correctly cleans up unless there was an error.
this relates to a previous bugfix of readLink which incorrectly returned
absolute paths ultimately rendering the Remove call also broken.
The added "aptly publish repo" option "-access-by-hash" publishes
the index files (Packages*, Sources*) also as hardlinked hashes.
Example:
/dists/yakkety/main/binary-amd64/by-hash/SHA512/31833ec39acc...
The Release files indicate this with the option "Acquire-By-Hash: yes"
This is used by apt >= 1.2.0 and prevents the "Hash sum mismatch" race
condition between a server side "aptly publish repo" and "apt-get update"
on a client.
See: http://www.chiark.greenend.org.uk/~cjwatson/blog/no-more-hash-sum-mismatch-errors.html
This implementation uses symlinks in the by-hash/*/ directory for keeping
only two versions of the index files and deleting older files
automatically.
Note: this only works with aptly.FileSystemPublishedStorage
Closes: #536
Signed-off-by: André Roth <neolynx@gmail.com>
Otherwise two index files are generated (source arch, "udeb" true/false) which end up
sharing same final filename, and empty one might overwrite "real" one.
