tests/test-issue522

convert: readd --filemap

To handle merges correctly, this revision adds a filemap_source class
that wraps a converter_source and does the work necessary to calculate
the subgraph we're interested in.

The wrapped converter_source must provide a new getchangedfiles method
that, given a revision rev, and an index N, returns the list of files
that are different in rev and its Nth parent.

The implementation depends on the ability to skip some revisions and to
change the parents field of the commit objects that we returned earlier.

To make the conversion restartable, we assume the revisons in the
revmapfile are topologically sorted.

#!/bin/sh

# In the merge below, the file "foo" has the same contents in both
# parents, but if we look at the file-level history, we'll notice that
# the version in p1 is an ancestor of the version in p2.  This test
# makes sure that we'll use the version from p2 in the manifest of the
# merge revision.

hg init repo
cd repo

echo foo > foo
hg ci -d '0 0' -qAm 'add foo'

echo bar >> foo
hg ci -d '0 0' -m 'change foo'

hg backout -d '0 0' -r tip -m 'backout changed foo'

hg up -C 0
touch bar
hg ci -d '0 0' -qAm 'add bar'

hg merge --debug
hg debugstate | grep foo
hg st -A foo
hg ci -d '0 0' -m 'merge'

hg manifest --debug | grep foo
hg debugindex .hg/store/data/foo.i