What does a mercurial revision with no parent mean?

Question

I have a Mercurial repository that is in a strange state now. This is what it looks like in TortoiseHG:

Answer 1

Another way to see this is if you did hg update null after committing rev. 53. For example, consider this sequence:

hg init foo
# create some files
hg addremove
hg commit -m "Revision 0"
# edit, edit, edit
hg commit -m "Revision 1"
hg update null
hg tag -m "Create tag v1.0.0.0" "v1.0.0.0"

At this point, hg log will show revision 2's parent as -1:0000000000. Since hg update null clears out the working directory, the only file in it would be .hgtags (just like you were seeing).

Did you have other tags prior to rev. 53? If my suspicion is correct, they would not be present in your rev. 54 .hgtags.