convert: don't drop missing or corrupt tag entries
Cleaning up the tags file could be a useful feature in some cases, so maybe
there should be a switch for this. However, the default hg -> hg convert tries
to maintain identical hashes (thus convert.hg.saverev is off by default, but is
on by default for other source types). It looks like _rewritesubstate() has a
`continue` in it, and therefore a similar problem.
I ran into this conversion divergence when a coworker "merged" two repositories
by copy/pasting all of the files from the source repo and massaging the code,
and forgetting to revert the .hg* files. That silently emptied the .hgtags file
after the conversion. (This isn't the manifest node bug Yuya has been helping
with- this occurred well after the bzr -> hg conversion and wasn't a merge
commit, which made it extra puzzling. That bug is still an issue.)
Set up
$ hg init repo
$ cd repo
Try to import an empty patch
$ hg import --no-commit - <<EOF
> EOF
applying patch from stdin
abort: stdin: no diffs found
[255]
No dirstate backups are left behind
$ ls .hg/dirstate* | sort
.hg/dirstate