Create a merge-wrapper script

To allow us the flexibility we want to determine which diff tool should be used for different file extensions, we need to break out the logic in to an external script. Below I have 2 samples of a merge script. I started with the .sh file (bottom), but changed over to the .js version (above that) since it is easier for me to maintain.

I haven't yet tried to run this on windows, but suspect we can wrap the merge-wrapper.js in a .cmd file calling it with Node.JS.

Customize the `merge-wrapper.js`

Extend with other diff tool support:

If you want to extend the script to add support for your own diff tool, just create a new function that returns an object following the pattern of the existing createP4MergeCommand or createOpenDiffCommand.
Modify which diff tool is used per extension:

If you want to change which tool is used per file extensions you can modify the diffLookup hash to map various extensions to whatever tool you setup.
Leave me a comment (either here – or in the gist) of what diff tool you added.

I'd be happy to take contributions of other diff tools in this gist if you leave a comment with yours…

#!/usr/bin/env node 'use strict'; /* #!/bin/bash # # Wrapper script for git mergetool # This requires ~/.gitconfig file to have # the following (adjusting for paths): # # [merge] # tool = merge_wrapper # [mergetool "merge_wrapper"] # cmd = $HOME/merge-wrapper.js "$BASE" "$LOCAL" "$REMOTE" "$MERGED" # # Save this script in your $HOME # # How to create p4merge command? # http://answers.perforce.com/articles/KB_Article/Command-line-P4Merge-on-Mac-OS-X */ // BASE=$1 // LOCAL=$2 // REMOTE=$3 // MERGED=$4 var path = require('path'); var spawn = require('child_process').spawn; var diffArgs = process.argv.slice(2); diffArgs = { BASE: diffArgs[0], LOCAL: diffArgs[1], REMOTE: diffArgs[2], MERGED: diffArgs[3], REST: diffArgs.slice(4), ALL: diffArgs.slice(0), }; var diffOptions; function createP4MergeCommand(args) { var result = { cmd: "p4merge", args: args.ALL }; // p4merge doesn't like to be called with the extra REMOTE=3/MERGED=4 // args so we lop them off before loading it up for images. if(isImage(args.BASE)) { result.args = [args.BASE, args.LOCAL]; } return result; } function createOpenDiffCommand(args) { var result = { cmd: "opendiff", args: [args.BASE, args.LOCAL] }; return result; } var isImage = function (path) { var imageExtensions = [ "bmp", "gif", "jpg", "jpeg", "png", "pbm", "pgm", "ppm", "tiff", "xbm", "xpm" ]; return imageExtensions.some(function (ext) { return new RegExp("." + ext + "$", 'i').test(path); }); }; function launch(diffOptions) { var cmd = spawn(diffOptions.cmd, diffOptions.args); cmd.stdout.on('data', function (data) { console.log(data); }); cmd.stderr.on('data', function (data) { console.error(data.toString()); }); cmd.on('close', function (code) { process.exit(code); }); } var diffLookup = { ".bmp": createP4MergeCommand, ".gif": createP4MergeCommand, ".jpg": createP4MergeCommand, ".jpeg": createP4MergeCommand, ".png": createP4MergeCommand, ".pbm": createP4MergeCommand, ".pgm": createP4MergeCommand, ".ppm": createP4MergeCommand, ".tiff": createP4MergeCommand, ".xbm": createP4MergeCommand, ".xpm": createP4MergeCommand, // EX: using different diff command // ".js": createOpenDiffCommand, "DEFAULT": createP4MergeCommand }; var fileExt = (path.extname(diffArgs.BASE) || '').toLowerCase(); diffOptions = (diffLookup[fileExt] || diffLookup.DEFAULT)(diffArgs); //console.log(diffOptions); launch(diffOptions);

Below was an attempt at using a bash script to manage what I do above, it'll work for some, but I didn't want to maintain this – prefer the JS version instead.

#!/bin/bash # # Wrapper script for git mergetool # This requires the .gitconfig file to have # the following (adjusting for paths): # # [merge] # tool = merge_wrapper # [mergetool "merge_wrapper"] # cmd = $HOME/merge-wrapper.sh "$BASE" "$LOCAL" "$REMOTE" "$MERGED" # # Save this script in your $HOME # # # How to create p4merge command? # http://answers.perforce.com/articles/KB_Article/Command-line-P4Merge-on-Mac-OS-X # BASE=$1 LOCAL=$2 REMOTE=$3 MERGED=$4 if [[ $BASE == *.png ]]; then echo "Image diff.."; CMD="p4merge "$BASE" "$LOCAL"" echo $CMD eval $CMD else #Finally, the default case: CMD="p4merge "$BASE" "$LOCAL" "$REMOTE" "$MERGED"" #CMD="opendiff "$BASE" "$LOCAL" -ancestor "$REMOTE" -mergeFile "$MERGED"" echo $CMD eval $CMD fi

Setup `~/.gitconfig`

Now that we've created our merge wrapper script we need to tell git how to use it.

Say we placed our merge script in the following directory: $HOME/dotfiles/tools/merge-wrapper.js. You can add the below to your ~/.gitconfig file and when you use git difftool our new merge-wrapper will be used to pick diff tools based on file extension.

[merge]
    tool = merge_wrapper
[mergetool "merge_wrapper"]
    cmd = $HOME/dotfiles/tools/merge-wrapper.js "$BASE" "$LOCAL" "$REMOTE" "$MERGED"

Create a merge-wrapper script

Customize the merge-wrapper.js

Setup ~/.gitconfig

Customize the `merge-wrapper.js`

Setup `~/.gitconfig`