Select git mergetool based on file type

Question

When running git mergetool, I'd like to have git select the merge tool used based on the file extension. How can I do this?

A similar question was asked here: Git: configure patterns for difftool and mergetool and the answer was to write a custom merge driver. However, it seems like this would be executed upon git merge, whereas I would like the merge tool to be chosen upon git mergetool.

It seems like there must be some way to specify this with .gitattributes, but I can't seem to figure out how. Any advice?

Answer 1

One solution (since my old answer isn't a good fit for mergetool) is to set as a mergetool a wrapper script.

git config --global merge.tool customMergeTool
git config --global mergetool.customMergeTool.cmd 'customMergeTool.sh \"$BASE\" \"$LOCAL\" \"$REMOTE\" \"$MERGED\"'

That wrapper script customMergeTool.sh would:

• check what $BASE is (in particular, its file extension)
• call the appropriate merge tool based on that extension
• return the exit status of that mergetool

Here is for instance the script that the OP elsevers came up with: merge-wrapper.