Avoiding conflicts in .hgtags

[Greg Ward]

On 08 December 2008, Arne Babenhauserheide said:
> Am Montag 08 Dezember 2008 19:52:14 schrieb Greg Ward:
> >   [merge-patterns]
> >   .hgtags = hgmergetags
> >
> >   [merge-tools]
> >   hgmergetags.args = $local $base $other > $output
> >
> > Script attached.  Feedback welcome.
> 
> I just tried it with groups and then skimmed over the code to see that it 
> needs the layout of .hgtags. 
> 
> What is your reason for not just checking if lines are equal, that way making 
> a merger for any kind of append/remove-only file? 

Because .hgtags is *not* an append/remove-only file: tags can be
changed.  The trick is that it *is* a context-free file; you can merge
three copies of .hgtags by looking at each tag in isolation from the
others.  Because the merge is content-based rather than textual, you
should only get conflicts when there is a real conflict.  (E.g. you and
I both modify a tag to point to a different changeset, or you modify it
and I delete it.)

It does seem that there ought to be one merge algorithm for all these
special .hg* files, but I don't know what it is.  Maybe it's not
possible.

        Greg