convert: fix history topology when using hg.tagsbranch
When using hg.tagsbranch, all conversions fail at
transcribing the source repo topology with conversion
scenarios interleaving:
- initial repo conversion,
- then upstream tag
- then later incremental conversion
The problem is caused by the usage of the last source
revid as source revid for the tagnode in the revision
map.
On a later incremental conversion, when resolving some
child commit of the true last source revid, convert
will parent the nodes to the tag node. If using
tagsbranch you get a bad topology where all incremental
commit nodes end up in the tag branch.
Analysis and test by Edouard Gomez <ed.gomez@free.fr>
merge: exclude common ancestor from --preview (
issue1818)