I like git difftool --dir-diff because it checks out the modified files to a temporary directory and executes diff tool with directory pathes.

On Unix and MacOS, git difftool --dir-diff create a symbolic link to the working directory if a right-hand file has the same SHA1 as the file in the working directory. It's very useful when we modify right-hand files with a difftool.

On Windows, instead of creating symbolic links, git difftool --dir-diff copy back right-hand files to working directory after difftool program exits. I want to use symlinks on Git for Windows like Unix and MacOS.

Quick Hack Patch

Environment: Git for Windows 1.8.3 and Windows 7 (64bit).

Patch for C:\Program Files (x86)\Git\libexec\git-core\git-difftool.

--- git-difftool    Sun Jun  2 11:28:06 2013
+++ git-difftool    Tue Jul  9 00:42:02 2013
@@ -283,7 +283,7 @@
            exit_cleanup($tmpdir, 1);
        }
        if ($symlinks) {
-           symlink("$workdir/$file", "$rdir/$file") or
+           !system("git", "mklink", "$workdir/$file", "$rdir/$file") or
            exit_cleanup($tmpdir, 1);
        } else {
            copy("$workdir/$file", "$rdir/$file") or
@@ -448,7 +448,7 @@
    my $indices_loaded = 0;

    for my $file (@worktree) {
-       next if $symlinks && -l "$b/$file";
+       next if $symlinks;
        next if ! -f "$b/$file";

        if (!$indices_loaded) {

Save this patch to somewhere, and run GitBash as administrator.

$ cd /c/Program\ Files\ \(x86\)/Git/libexec/git-core/
$ patch < ~/git-difftool.patch
patching file `git-difftool'

Create a file on C:\Program Files (x86)\Git\libexec\git-core\git-mklink:

#!/bin/sh

cmd.exe /c "mklink \"$2\" \"$1\"" > /dev/null

(This script is necessary for converting /tmp/ directory to Windows path)

How to Use

First, configure difftool on .gitconfig. For example, set WinMerge as difftool.

[diff]
    tool = winmerge
[difftool winmerge]
    path = C:/Program Files (x86)/WinMerge/winmergeu.exe
    cmd = \"C:/Program Files (x86)/WinMerge/winmergeu.exe\" -r -u \"$LOCAL\" \"$REMOTE\"

Run GitBash as an administrator, and enter following command.

$ git difftool -d --symlinks [<commit> [<commit>]]

(On Windows, administrator privileges is required to create symbolic links)

If you want, create an alias on .gitconfig.

[alias]
    d = difftool -d --symlinks

Enjoy.