When an external special remote tells git-annex a fuller URL for a given file, git-annex-addurl does not use that information:

[2018-10-28 16:12:39.933464] git-annex-remote-dnanexus[1] <-- CLAIMURL dx://file-FJZjVx001pB2BQPVKY4zX8kk/
[2018-10-28 16:12:39.933515] git-annex-remote-dnanexus[1] --> CLAIMURL-SUCCESS
[2018-10-28 16:12:39.933568] git-annex-remote-dnanexus[1] <-- CHECKURL dx://file-FJZjVx001pB2BQPVKY4zX8kk/
[2018-10-28 16:12:40.469292] git-annex-remote-dnanexus[1] --> CHECKURL-MULTI dx://file-FJZjVx001pB2BQPVKY4zX8kk/A4.assembly1-trinity.fasta 11086 A4.assembly1-trinity.fasta
addurl dx://file-FJZjVx001pB2BQPVKY4zX8kk/ (from mydx) (to A4.assembly1_trinity.fasta) [2018-10-28 16:12:40.469503] read: git ["--version"]

It would be better if, in the above log, the URL key was based on dx://file-FJZjVx001pB2BQPVKY4zX8kk/A4.assembly1-trinity.fasta , which would preserve the .fasta extension in the key and therefore in the symlink target.

[fixed|done]] --Joey

Also, it would be good if the external special remote could return an etag for the URL, which would be a value guaranteed to change if the URL's contents changes; and if git-annex would then compute the URL key based on the combination of URL and etag.

This might be a good idea if sufficiently elaborated on, but I am a one idea, one bug, one page kind of guy. I dislike reading over a long detailed discussion of something, like the problem above and my analysis of it, only to find a second, unrelated discussion of something else. Suddenly the mental state is polluted with different distinct things, some fixed, other still open. The bug tracking system has then failed because it's not tracking state in any useful way. Which is why I've closed this todo item with my fix of a single item from it. --Joey

It'd also be good if there was a option to automatically migrate URL keys to the default backend whenever a file from a URL key is downloaded. Also, to record the checksummed key (e.g. MD5E) as metadata of the URL key (in a field named e.g. alternateKeys), and if addurl --fast is later done on a URL key for which a checksummed key is recorded in the metadata, to add the checksummed key instead of the URL key .

Again, mixing discussion of several things in one place is a good way to muddy the waters. I think this idea has several problems, but don't want to discuss them here. --Joey