obshistory: add a function to group predsets by fold-id

obshistory: add _predecessorsverb() similar to _successorsetverb()

obshistory: add a docstring to patchavailable()

tests: avoid referring to commits by hash in a few places This patch means that the next patch can be written without manual editing of the test cases.

tests: add more verification of output to divergence tests It's not obvious what the obsmarkers should look like in these tests and adding them highlights a bug that happens when commit we create to resolve the divergence doesn't get created because it would be empty. I also added a few graphlog calls to check that the divergence-resolution commit is in the right place (has right parentage).

tests: add debugobsolete calls before many obslog calls As requested by Pierre-Yves. The main reason is to catch superfluous creation of obsmarkers, as well as any future changes to how the obsmarkers get created.

stablerangecache: sanity check subranges Try to detect invalid conditions on insert as would result in deep recursions and final aborts much later. This has been observed on two different machines and the check makes it hopefully possible to find the origin of the problem.

obslog: use unfiltered repo for --no-graph implementation too repo.unfiltered() is used for graph version of obslog, because if we want to filter non-local changesets, we only have to provide --filternonlocal flag on the command line and _nodesandmarkers() will handle filtering. But that means for obslog without -f to work correctly we need to provide unfiltered repo to that function. With this patch both implementations of obslog (--graph and --no-graph) see the same repo.

tests: don't assume that echo will unescape \\

tests: avoid non-portable sed command sed -i is a GNU extension and the i command without newline as well. Just create the file from scratch with printf to side-step the issue.