Feature request : avoid unecessary HTTP mirror update when nothing changed

[pladen]

(First thank you Aptly team for this great tool !)

Found myself in a work where I have to mirror several repositories, then filter, merge and publish a new one.
These repo are updated on really different ways : some are updated 4 times a day, while other only change on a monthly basis.
Every time my script invoke "aptly mirror update", it can't take a very long time depending on the network conditions.

To improve my script execution time I had to create a small shell script around "aptly mirror update" to avoid updating unchanged mirror.

Something like (pseudo code):
TIMECOND = $(aptly mirror show -json $REPONAME | jq -r .LastDownloadDate)
Then :

CODE=$(curl --head --time-cond $TIMECOND $REPO_URL/Release)
if [ $CODE -eq 304 ] ; then exit 0 ; fi

It would be great to have this feature directly in Aptly.

It could be done by adding a header on the metadata HTTP get request, with the already known lastDownloadDate :
If-Modified-Since: Fri, 21 Aug 2026 12:08:56 UTC

And deal with the answer either 200 (new file, go on) or 304 (unchanged, skip download)