How do I pipe in FileMerge as a diff tool with git on OS X?

Question

I'm new to git on OS X, and I'm using it via the command line. I come from the world of Tortoise SVN and Beyond Compare on Windows.

I want to be able to send diffs to FileMerge.

I was able to do this with TextMate simply by using:

git diff | mate

But I'm not sure how to get that set up so I can use FileMerge instead?

Answer 1

Here's a script (originally by Toby White) that I hacked up to compare the entire directory structure in FileMerge rather than opening each file individually.

#!/bin/sh
#
# This script was written by Toby White under an unknown license, and published
# on the Git mailing list:
#
#   http://kerneltrap.org/mailarchive/git/2007/11/21/435536
#
# Superficial changes were made by Nathan de Vries to allow the script to be
# run under Leopard.
#
# Adapted by Daniel Miller : http://stackoverflow.com/a/12957945/10840
# - allow changes to be saved back to the working copy when diffing against HEAD
# - work when FileMerge is already open
# - always compare archived copies so ignored files are excluded from the diff
# - allow diff of unstaged changes (no arguments); creates a dangling commit
# - allow diff of subdirectory within the repo
#
# Known issues:
# - Always uses the same two directories (/tmp/git-opendiff-old and
#   /tmp/git-opendiff-new); THEY WILL BE DELETED IF THEY ALREADY EXIST.
#   Ugly, I know, but it makes the script work even if FileMerge is open.

OLD=
NEW=
FILEPATH=
HAS_ARGS=no
IGNORE_TO_PATH=no

# loosely based on https://stackoverflow.com/a/14787208/10840
while [ "$#" -ge 1 ]; do
    HAS_ARGS=yes
    case "$1" in
        -h)
            echo "usage: $0 [--cached | <ref> [<ref>]] [-- <path>]"
            exit 0
            ;;
        --cached)
            # diff staged changes
            NEW=$(git write-tree)
            OLD=HEAD
            IGNORE_TO_PATH=yes
            shift
            ;;
        --)
            shift
            FILEPATH="$@"
            break
            ;;
        *)
            if [[ "$IGNORE_TO_PATH" == "no" ]]; then
                if [ -z "$OLD" ]; then
                    OLD="$1"
                else
                    NEW="$1"
                    IGNORE_TO_PATH=yes
                fi
            fi
            shift
            ;;
    esac
done
if [ -z "$OLD" ]; then
    OLD=HEAD
fi
if [[ "$HAS_ARGS" == "no" ]]; then
    # diff unstaged changes
    # http://stackoverflow.com/a/12010656/10840
    NEW=$(git stash create)
    echo "diff unstaged changes"
fi

TMP_OLD=/tmp/git-opendiff-old
TMP_NEW=/tmp/git-opendiff-new
test -d $TMP_OLD && rm -rf $TMP_OLD; mkdir $TMP_OLD
test -d $TMP_NEW && rm -rf $TMP_NEW; mkdir $TMP_NEW

TMP_OLD=$TMP_OLD/$OLD; mkdir -p $TMP_OLD
git archive --format=tar $OLD $FILEPATH | (cd $TMP_OLD; tar xf -)

if test -z "$NEW"; then
    SAVE_TO=$(git rev-parse --show-cdup)
    test -z "$cdup" && SAVE_TO=.
    git archive --format=tar HEAD $FILEPATH | (cd $TMP_NEW; tar xf -)
    opendiff $TMP_OLD/$FILEPATH $TMP_NEW/$FILEPATH -merge $SAVE_TO &> /dev/null &
else
    TMP_NEW=$TMP_NEW/$NEW; mkdir -p $TMP_NEW
    git archive --format=tar $NEW $FILEPATH | (cd $TMP_NEW; tar xf -)
    opendiff $TMP_OLD/$FILEPATH $TMP_NEW/$FILEPATH &> /dev/null &
fi

Put this somewhere on your path. I prefer ~/bin/git-opendiff, which means git opendiff ... works as expected.

Update: diff unstaged changes when called with no arguments, added -h (help) option.

Update: diff subdirectory with -- <path>. Also better argument parsing.

Answer 2

Although it's not exactly the same as piping stdin into a script, you can do this:

git difftool -t opendiff -y

That will launch FileMerge once for each file. Doing the whole project tree at once takes a little scripting.

See also this question.

Answer 3

Create an executable script git-diff-cmd.sh

#!/bin/bash

xattr -w com.apple.TextEncoding "UTF-8;134217984" "$2"
xattr -w com.apple.TextEncoding "UTF-8;134217984" "$5"

/usr/bin/opendiff "$2" "$5" -merge "$1"

Now edit your .gitconfig file to include the lines

[diff]
    external = <path-to>/git-diff-cmd.sh

...replacing <path-to> by the path to git-diff-cmd.sh. Now git diff will use FileMerge, and correctly display UTF-8 Unicode characters.

Answer 4

I don't know what's happening to me since I updated OS X and now opendiff is not working as it used to be. So I copied this script from here and it worked.

#!/bin/sh 
dir=$PWD
until [ -e "$dir/.git" ]; do
  if [ "$dir" == "/" ]; then
    echo "Not a git repository" >&2
    exit 1;
  fi
  dir=`dirname "$dir"`
done
open -a FileMerge -n -W --args -left "$dir/$1" -right "$2" -merge "$5"

Answer 5

First, start by telling git you want to use FileMerge (aka opendiff) as your default difftool:

git config --global diff.tool 

(This only needs to be done once)

Then it's as simple as

git difftool