How to use an external diff tool for Git in Visual Studio 2013?

Question

I've found this post that explains how you can have Visual Studio 2013 use the built-in diff tool when comparing files in Git, but I'm having the opposite problem. Right now when I right-click on a file in the Git Commit Details window and choose Compare With Previous... VS performs the diff in the default Visual Studio 2013 compare tool, but I want it to use an external diff tool, specifically TortoiseMerge.exe. I have it specified in my C:\Users\[My Name]\.gitconfig and it works properly from the GitBash console, but Visual Studio ignores this setting and always uses its built-in tool.

This is what I have in that .gitconfig:

[merge]
    tool = kdiff3
[mergetool "kdiff3"]
    path = c:/Program Files (x86)/KDiff3/kdiff3.exe
[diff]
    guitool = TortoiseMerge
[difftool "TortoiseMerge"]
    path = C:/Program Files/TortoiseSVN/bin/TortoiseMerge.exe

I have also checked my local repository's .gitconfig to make sure it wasn't overriding this setting, and it does not specify any diff or difftool settings.

I have also tried similar settings in my .gitconfig like:

[diff]
    guitool = TortoiseMerge
[difftool "TortoiseMerge"]
    cmd = \"C:/Program Files/TortoiseSVN/bin/TortoiseMerge.exe\" /base:"$REMOTE" /local:"$MINE"

but the behavior does not change.

Answer 1

Visual Studio uses the diff.tool configuration setting, not the diff.guitool configuration setting.

Try:

[diff]
    tool = TortoiseMerge

Answer 2

I have had the same issue recently in Visual Studio 2012. I will post the solution here as this is the first thread I found when searching.

My .gitconfig file looked like this:

[merge]
    tool = kdiff3
[diff]
    tool = kdiff3
[difftool]
    prompt = true

[difftool "kdiff3"]
    path = "C:/Program Files/KDiff3/kdiff3.exe"
    keepBackup = false
    trustExitCode = true
[mergetool]
    prompt = true

[mergetool "kdiff3"]
    cmd = "C:/Program Files/KDiff3/kdiff3.exe" $BASE $LOCAL $REMOTE -o $MERGED
    keepBackup = false
    trustExitCode = true

[mergetool "vsdiffmerge"]
    cmd = "C:/Program Files (x86)/Microsoft Visual Studio 12.0/Common7/IDE/vsdiffmerge.exe" /m $REMOTE $LOCAL $BASE $MERGED
    keepbackup = false
    trustexistcode = true

The problem was the newlines between config sections.

Changing the file to this worked correctly:

[merge]
    tool = kdiff3
[diff]
    tool = kdiff3
[difftool]
    prompt = true
[difftool "kdiff3"]
    path = "C:/Program Files/KDiff3/kdiff3.exe"
    keepBackup = false
    trustExitCode = true
[mergetool]
    prompt = true
[mergetool "kdiff3"]
    cmd = "C:/Program Files/KDiff3/kdiff3.exe" $BASE $LOCAL $REMOTE -o $MERGED
    keepBackup = false
    trustExitCode = true
[mergetool "vsdiffmerge"]
    cmd = "C:/Program Files (x86)/Microsoft Visual Studio 12.0/Common7/IDE/vsdiffmerge.exe" /m $REMOTE $LOCAL $BASE $MERGED
    keepbackup = false
    trustexistcode = true