hgext/largefiles/CONTRIBUTORS

revset: add destination() predicate

This predicate is used to find csets that were created because of a graft,
transplant or rebase --keep.  An optional revset can be supplied, in which case
the result will be limited to those copies which specified one of the revs as
the source for the command.

    hg log -r destination()                 # csets copied from anywhere
    hg log -r destination(branch(default))  # all csets copied from default

    hg log -r origin(x) or destination(origin(x))  # all instances of x

This predicate will follow a cset through different types of copies.  Given a
repo with a cset 'S' that is grafted to create G(S), which itself is
transplanted to become T(G(S)):

    o-S
   /
  o-o-G(S)
   \
    o-T(G(S))

    hg log -r destination( S )    # { G(S), T(G(S)) }
    hg log -r destination( G(S) ) # { T(G(S)) }

The implementation differences between the three different copy commands (see
the origin() predicate) are not intentionally exposed, however if the
transplant was a graft instead:

	hg log -r destination( G(S) )   # {}

because the 'extra' field in G(G(S)) is S, not G(S).  The implementation cannot
correct this by following sources before G(S) and then select the csets that
reference those sources because the cset provided to the predicate would also
end up selected.  If there were more than two copies, sources of the argument
would also get selected.

Note that the convert extension does not currently update the 'extra' map in its
destination csets, and therefore copies made prior to the convert will be
missing from the resulting set.

Instead of the loop over 'subset', the following almost works, but does not
select a transplant of a transplant.  That is, 'destination(S)' will only
select T(S).

    dests = set([r for r in subset if _getrevsource(repo, r) in args])

Greg Ward, author of the original bfiles extension
Na'Tosha Bard of Unity Technologies
Fog Creek Software
Special thanks to the University of Toronto and the UCOSP program