Re: [Gnu-arch-users] Re: libraries / cacherevs

[Tom Lord]

    > From: Stefan Monnier <address@hidden>

    > BTW, what are those hardlinks used for?

    > Why not only keep the currently-non-hardlinked files (and rely on the
    > inventory to discover that the file exists in the revision and then look
    > for older revs in the lib if you ever need to look at that file).


There are three reasons.

One is simply convenience.   By using hardlinks, you get a complete
tree that all tools understand rather than only tools that understand
the format of an arch revision library.


Another is storage management.   Suppose that I have two trees
sharing a common file.   With hardlinks, I can delete either tree and
the other is still valid.   Without hardlinks, if I delete one of the
trees, then the revision library no longer contains all of the files
needed for the other.

A third is good performance without code complexity.   Naively
implementing a user-space directory stack (which is what you're
describing) would be comparatively slow for common operationos like
mkpatch or get.   It can surely be optimized but the incentives for
doing so in this case are relatively slight.



-t