$GENTOO_MIRRORS in /etc/make.conf is allowed to contain local filesystem paths.
Unfortunately, mirrorselect removes such paths, requiring the admin to manually
re-insert those paths into GENTOO_MIRRORS after mirrorselect has been run.
Reproducible: Always
Steps to Reproduce:
1. Prefix GENTOO_MIRRORS with something like "/usr/local/portage/distfiles "
2. Run "mirrorselect".
Actual Results:
The prefix is lost.
Expected Results:
All leading GENTOO_MIRRORS entries which do not look like some URI syntax
should be retained.
When writing private ebuilds in an overlay for the local host only, it is
common to add a directory like /usr/local/portage/distfiles before the first
mirror listed in $GENTOO_MIRRORS.
Unfortunately, mirrorselect removes such entries, and so the admin has to
manually re-insert them.
I would suggest parsing the old $GENTOO_MIRRORS value, split it into words and
remember all such leading words which start with a slash (and are therefore
local paths).
Then mirrorselect should do what it does now. But before writing back the newly
detected GENTOO_MIRRORS, the saved paths should be inserted before the first
actual mirror.
