This is a refactor and refresh of the code used to find where we should
download packages.
* Incorporate suggestions from FS#25435 to use TMPDIR from the
environment if set, otherwise fall back to /tmp as before.
* Make the writability tests a bit more in depth. We now do a three part
check consisting of:
- S_ISDIR(): is this even a directory
- access(W_OK): is this directory writable by the current user.
Unfortunately for root, this almost always returns that it is, but
in the case of a RO mount or NFS share inaccessible to root, this
check will exclude the directory.
- mode & (any write bit): is there a writable bit set on this
directory. This makes it possible to enforce a read-only cache
directory by setting permissions to 0555, for example.
Signed-off-by: Dan McGee <dan@archlinux.org>
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