convert: allow the converter_source to say "skip this revision"
If getchanges returns a string, it's assumed to be the id of an
already converted revision. We map the current revision to the same
revision this converted revision was mapped to.
To allow skipping a root revision, getchanges can return the special
string 'hg-convert-skipped-revision' (a.k.a. common.SKIPREV), which
hopefully won't clash with any real id.
The converter_source is responsible for rewriting the parents of the
commit objects to make sure the revision graph makes sense.
#!/bin/sh
mkdir t
cd t
hg init
mkdir a
echo foo > a/a
echo bar > a/b
hg add a
hg ci -m "0" -d "0 0"
hg co -C 0
hg mv a b
hg ci -m "1 mv a/ b/" -d "0 0"
hg co -C 0
echo baz > a/c
hg add a/c
hg ci -m "2 add a/c" -d "0 0"
hg merge --debug 1
echo a/* b/*
hg st -C
hg ci -m "3 merge 2+1" -d "0 0"
hg debugrename b/c
hg co -C 1
hg merge --debug 2
echo a/* b/*
hg st -C
hg ci -m "4 merge 1+2" -d "0 0"
hg debugrename b/c