Messages in this thread | | | From | "Lou Grinzo" <> | Subject | FS union | Date | Wed, 16 Jun 1999 08:32:57 -0400 |
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One possibility that I don't think anyone has mentioned is giving the user or programmer finer-grained control over the name space for the unioned FS's. In other words, there could easily be times when you would want to make just certain files in the underlying FS take precedence in the name space.
The basic model talked about so far, of "last mounted, first found" is good. But adding a way (from the CL as well as a sys call) to explicitly say "if fred.c is in the underlying FS, make it take precedence over the fred.c, if any, in the top FS" would be very handy. Imagine being able to union the source trees for two versions of a project, and selectively use some files from the underlying project's FS in the top project, without having to cp source files or change make files, for example.
You'd want a corresponding way to undo this, and "sink" fred.c again, as well as some other tools or options on existing tools, to help the disambiguate the name space.
One other thing - has a decision been made about the number of FS's that can be unioned (unified?) at once? Everyone keeps talking about two FS's in examples (as I did above), but is there a technical reason to limit it to two, or will it be more?
Lou
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