Capture 'mount points' are confusing.

[mornfall]

There's a few issues to deal with:

• mount points (both files and directories) are created automatically, but not their parents
• hence, the parent of a mount point must exist (that is it's either /, or it was created by an earlier capture)
• normal mount points hide whatever was under the directory, but we go the opposite way: whatever is captured first under a given path wins (we also merge contents of different captures)

It might be prudent to use real 'mount' semantics (but this interferes oddly with the 'follow' mode of symlink capture).

[mornfall]

Milestone renamed