HOWTO: Using FileMerge (opendiff) with Git on OSX

howto-filemerge-git-osx.md

HOWTO: Using FileMerge (opendiff) with Git on OSX

FileMerge (opendiff) can really come in handy when you need to visually compare merging conflicts. Other times it's just a nice visual way to review your days work.

The following method works by creating a simple bash script (git-diff-cmd.sh) that sets us up with the proper command line arguments for Git to pass off files to FileMerge.

1. Open the bash script for editing:

    vi ~/bin/git-diff-cmd.sh
   

2. Paste the following code:

    #!/bin/sh 
    /usr/bin/opendiff "$2" "$5" -merge "$1"
   

3. Make the bash script executable:

    chmod +x ~/bin/git-diff-cmd.sh
   

4. Tell Git (globally) to run our bash script when 'git diff' is issued:

    git config --global diff.external ~/bin/git-diff-cmd.sh
   

Now head over to your Git-aware project directory and issue a git diff /path/to/modified/file.py and FileMerge will pop up showing you the differences against it and HEAD.

You can also do things like git diff --cached to review all the changes against HEAD.

git config --global alias.opendiff difftool --no-prompt --tool opendiff --dir-diff

this did not work for me. just outputs the usage text.

Add quotes to the aliased command:

git config --global alias.opendiff "difftool --no-prompt --tool opendiff --dir-diff"

can you have opendiff without installing the whole XCode app? (which is huge)

I don’t think running opendiff is possible without Xcode, unfortunately. See top answer on this thread: https://apple.stackexchange.com/questions/108025/is-it-possible-to-use-filemerge-as-standalone-app

Filemerge sucks. Pasting in lines of text it always deletes out all the whitespace.