Hello, Helen.
That chromAlias file should now be available on our download server:
https://hgdownload.soe.ucsc.edu/goldenPath/hg19/bigZips/p13.plusMT/.
As to your question about the purpose of "hgdownload-test," it serves as a place to test changes to pages on our download server and as a staging area for many files before they are reviewed and pushed to our primary download server. While many of the files do eventually make it to our primary download server, some don't for one reason or another. For example, it can simply be that they were overlooked, as was the case here, or they're superseded by newer data before they can be reviewed and pushed.
If you have any further questions, please reply to
gen...@soe.ucsc.edu. All messages sent to that address are archived on a publicly-accessible Google Groups forum. If your question includes sensitive data, you may send it instead to
genom...@soe.ucsc.edu.
Matthew Speir
UCSC Genome Browser, User Support