maildir / read-tree trivial merging getting in the way?

I've spent a few hours playing round with maildir-aware merging.

The basic idea I'm trying to implement is to flip the index round so that instead of looking at how the content has changed for a particular filename, I'm looking at how the filenames have changed for a particular content.

So I'm using git read-tree -m to populate the index with entries for the branches to merge so that I can then diddle round with those.

But the read-tree trivial merge logic seems to be getting in the way a bit.

In my test repo, I have two branches ('master' and 'red') forked from the base point 'base':

in 'base':

$ ls A fish one

in 'red':

$ ls B billygoat one

in 'master'

$ ls A lion two

and fish to billygoat and lion to give the above.

When I read in the tree I get automatic resolving (down to stage 0) for the added files. But actually in the output of my merge, I'm not always going to want that to happen: In the A->B case, I do want to keep B (and need to remove A), likewise in the one->two case.

But for fish->{billygoat,lion}, I only want one file to end up at stage 0, and it might not be called either billygoat or lion - in maildir, the filenames are more structured, and given a filename like foo:2,SR and foo:2,SF I would want to compose the filenames to give me foo:2,SRF.

$ git read-tree -m base master red

$ git ls-files --stage 100644 40e0a6f540b1b457c61315f3ccf2f5ed628e2f36 1 A 100644 40e0a6f540b1b457c61315f3ccf2f5ed628e2f36 2 A 100644 40e0a6f540b1b457c61315f3ccf2f5ed628e2f36 0 B 100644 a8150e61a3a4c9941d29169ee639396547f40de2 0 billygoat 100644 a8150e61a3a4c9941d29169ee639396547f40de2 1 fish 100644 a8150e61a3a4c9941d29169ee639396547f40de2 0 lion 100644 b67e17aeb5938def7ee105c2afe9fbb30a28a872 1 one 100644 b67e17aeb5938def7ee105c2afe9fbb30a28a872 3 one 100644 b67e17aeb5938def7ee105c2afe9fbb30a28a872 0 two

Now, I think maybe I can just look at what has made it to stage 0 and play round with those, but it makes me feel a little dirty - if anything, the index indicates that a bunch of stuff has been correctly merged (by being at stage 0) when in fact it hasn't.

So basically my question is: should I feel dirty about doing this and diddle read-tree so that there's a flag to not do the trivial merges automatically?