Created attachment 5008 [details] irc conversation if premirror's shallow clone contains SRCREV but the one in download dir doesn't then premirror is not used for downloading but upstream instead. Reported in irc. See attachement
The problem is in this call: https://github.com/yoctoproject/poky/blob/master/bitbake/lib/bb/fetch2/git.py#L378 FETCH_HEAD is not part of "git branch --contains" lookup.
https://git.openembedded.org/bitbake/commit/?h=master-next&id=d6fac83c4e36a6db4f02e4690fe08b78363c4dd5