inline-changelog: fix a critical bug in write_pending that delete data Since a93e52f0b6ff we no longer use inline-revlog for the changelog. The goal there was to solve the lack of testing for the two variants (inline vs split) and reduce the complexity of the interaction with "diverted-write" on the changelog level. However many existing repository still have inline-changelog and we automatically move them to normal revlog as soon as we have the chances. Unfortunately This conversion is buggy and can result in the destruction of the changelog.i if hook triggers the "write pending" mechanism. The bugs comes from the "revlog splitting" logic and the "write_pending" logic stepping over each other. Ironically the change in a93e52f0b6ff aims at no longer having this kind of problem. This changesets fix this issue and add associated tests. Fixing this reveal that the transaction hooks end up not seeing the pending transaction content, because the name is not right ("changelog.i.s.a" instead of "changelog.i.s") we fix this in the next changeset.