Re: [PATCH] merge-file: add --diff-algorithm option

Hi all,

Here a few more thoughts about this patch, to explain what brought me to needing that. If this need is misguided, perhaps you could redirect me to a better solution.

I am writing a custom merge driver for Java files. This merge driver internally calls git-merge-file and then solves the merge conflicts which only consist of import statements (there might be cases where it gets it wrong, but I can then use other tools to cleanup those import statements). When testing this, I noticed that the merge driver performed more poorly on other sorts of conflicts, compared to the standard "ort" merge strategy. This is because "ort" uses the "histogram" diff algorithm, which gives better results than the "myers" diff algorithm that merge-file uses.

Intuitively, if "histogram" is the default diff algorithm used by "git merge", then it would also make sense to have the same default for "git merge-file", but I assume that changing this default could be considered a bad breaking change. So I thought that making this diff algorithm configurable would be an acceptable move, hence my patch.

Of course, the diffing could be configured in other ways, for instance with its handling of whitespace or EOL (similarly to what the "git-diff" command offers). I think those options would definitely be worth exposing in merge-file as well. If you think this makes sense, then I would be happy to work on a new version of this patch which would attempt to include all the relevant options. I could also try to add the corresponding tests.

But perhaps my need is misguided? Could it be that I should not be writing a custom merge driver, but instead use another extension point to only process the conflicting hunks after execution of the existing merge driver? I couldn't find such an extension point, but it can well be that I missed it.

Thank you,

Antonin