Configuring diff tool with .gitconfig

How do I configure Git to use a different tool for diffing with the .gitconfig file?

I have this in my .gitconfig:

[diff]
    tool = git-chdiff #also tried /bin/git-chdiff

It does not work; it just opens the regular command line diff. When I do

export GIT_EXTERNAL_DIFF=git-chdiff

then git diff will open up the external diffing tool (so I know the external diff tool script works fine). Do I have something wrong with my .gitconfig configuration for the diff tool?

An additional way to do that (from the command line):

git config --global diff.tool tkdiff
git config --global merge.tool tkdiff
git config --global --add difftool.prompt false

The first two lines will set the difftool and mergetool to tkdiff- change that according to your preferences. The third line disables the annoying prompt so whenever you hit git difftool it will automatically launch the difftool.

Git offers a range of difftools pre-configured "out-of-the-box" (kdiff3, kompare, tkdiff, meld, xxdiff, emerge, vimdiff, gvimdiff, ecmerge, diffuse, opendiff, p4merge and araxis), and also allows you to specify your own. To use one of the pre-configured difftools (for example, "vimdiff"), you add the following lines to your ~/.gitconfig:

[diff]
    tool = vimdiff

Now, you will be able to run "git difftool" and use your tool of choice.

Specifying your own difftool, on the other hand, takes a little bit more work, see How do I view 'git diff' output with my preferred diff tool/ viewer?

Others have done a 99% answer on this, but there is one step left out. (My answer will be coming from OS X so you will have to change file paths accordingly.)

You make these changes to your ~/.gitconfig:

[diff]
    tool = diffmerge
[difftool "diffmerge"]
    cmd = /Applications/Diffmerge.app/Contents/MacOS/diffmerge $LOCAL $REMOTE

This will fix the diff tool. You can also fix this without editing the ~/.gitconfig directly by entering these commands from the terminal:

git config --global diff.tool diffmerge
git config --global difftool.diffmerge.cmd "/Applications/DiffMerge.appContents/MacOS/diffmerge \$LOCAL \$REMOTE"

The 1% that everyone else failed to mention is when using this you can't just run git diff myfile.txt; you need to run git difftool myfile.txt.

Reproducing my answer from this question which was more specific to setting Beyond Compare as diff tool for Git. All the details that I've shared are equally useful for any diff tool in general, so I am sharing it here.

The first command that we run is as below:

git config --global diff.tool bc3

The above command creates below entry in .gitconfig file found in %userprofile% directory:

[diff]
    tool = bc3

%userprofile% is an environment variable which you can type on Run prompt and hit Enter to open the directory location where .gitconfig file is present.

That's it. This is all you required while setting up an already published version of any well-known comparison tool which is already known to Git like in this case 3rd version of Beyond Compare is known to Git.

Let's do a deep-dive now!

Additionally, you might be required to run the below command also:

git config --global difftool.bc3.path "c:/program files/beyond compare 3/bcomp.exe"

Running this command is optional. It is required in some specialized cases only. We will know its reason in a short while from now.

The most important thing to know here is the key bc3. This is a well-known key to Git which maps to a particular version of a specific comparison tool available in market e.g. in this case bc3 corresponds to 3rd version of Beyond Compare tool. If you want to see complete list of the keys maintained by Git then run below comand on Git Bash command-line:

git difftool --tool-help

When we run above command then it returns below list:

vimdiff
vimdiff2
vimdiff3
araxis
bc
bc3
codecompare
deltawalker
diffmerge
diffuse
ecmerge
emerge
examdiff
gvimdiff
gvimdiff2
gvimdiff3
kdiff3
kompare
meld
opendiff
p4merge
tkdiff
winmerge
xxdiff

While setting up a comparison tool for Git, we can use any of the above pre-existing keys based on the tool and its version you're using e.g. for Beyond Compare v1 we'll use the key bc, for Beyond Compare v3 we'll use the key bc3.

But in some cases, we might have to define a brand new key of our own e.g. let's say we're setting-up a brand new comparison tool which has just been released to market. For obvious reasons the current version of Git installed on your machine will not show any key corresponding to this new tool. Eventually Git will show it in a future release but not immediately. Similarly, this problem can occur for a newly released version of an existing tool also e.g. there is no key for Beyond Compare v4 in above list. So you are always free to map any tool to any of pre-existing keys or to a new custom key of your own.

Now let us understand below scenarios for while setting up a comparison tool which is:

• A new version of an old tool has got released which is not mapped to any pre-defined keys in Git?

OR

• Absolutely new in market

Like in my case, I had installed Beyond Compare v4. Beyond Compare tool is already known to Git but its version 4 release is not mapped to any of the existing keys. So we can follow any of the below approaches:

1. Since no key exists in Git for Beyond Compare v4 so we can map it to the already existing key bc3 even though it is meant to be mapped to Beyond Compare v3. We can outsmart Git to save some effort.

   Now here is the answer to the question we left unanswered in the first paragraph - If you map any tool to the key which is already known to Git then you would not need to run the second command. This is because the tool's EXE location is already known to Git.

   But remember, this will work only when the EXE location of the tool doesn't change across versions. If Beyond Compare v3 and v4 have different install locations in %programfiles% directory then it becomes mandatory to run the second command.

   For e.g. if I had installed Beyond Compare v3 on my box then having below configuration in my .gitconfig file would have been sufficient to complete the setup process. This is based on the assumption that v3 and v4 will have same install path.

   [diff]
   tool = bc3
   

   But if we want to associate the non-default tool then we need to mention the path attribute separately so that Git will know the path of EXE from where it has to be launched. Below entry tells Git to launch Beyond Compare v4 instead. Note the EXE's path:

   [difftool "bc3"]
   path = c:/program files/Beyond Compare 4/bcomp.exe
   

   Also, if we wanted we could have mapped Beyond Compare v4 to any of the pre-defined keys of other tools as well e.g. examdiff. Git won't stop you from doing this bad thing. Although we should not do so avoid a maintenance nightmare.

2. Cleanest approach is to define a custom key. We can define a brand new key for any new comparison tool or a new version of an old tool. Like in my case I defined a new key bc4 as it is fairly intuitive. I could have named it foobaar.

   Now when the key is absolutely new, the setup process is slightly different. In this case you have to run two commands in all. But our second command will not be setting path of our new tool's EXE. Instead we have to set cmd attribute for our new tool as shown below:

   git config --global diff.tool bc4
   
   git config --global difftool.bc4.cmd "\"C:\\Program Files\\Beyond Compare 4\\bcomp.exe\" -s \"\$LOCAL\" -d \"\$REMOTE\""
   

   Running above commands creates below entries in your .gitconfig file:

   [diff]
   tool = bc4
   
   [difftool "bc4"]
   cmd = \"C:\\Program Files\\Beyond Compare 4\\bcomp.exe\" -s \"$LOCAL\" -d \"$REMOTE\"
   

I would strongly recommend you to follow approach # 2 to avoid any maintenance issues in future.

Here's the part of my ~/.gitconfig where I configure diff and merge tools. I like diffmerge by SourceGear. (I like it very very much, as a matter of fact).

[merge]
        tool = diffmerge
[mergetool "diffmerge"]
        cmd = "diffmerge --merge --result=\"$MERGED\" \"$LOCAL\" \"$(if test -f \"$BASE\"; then echo \"$BASE\"; else echo \"$LOCAL\"; fi)\" \"$REMOTE\""
        trustExitCode = false
[diff]
        tool = diffmerge
[difftool "diffmerge"]
        cmd = diffmerge \"$LOCAL\" \"$REMOTE\"

So, you see, you're defining a tool named "diffmerge" in the [difftool "diffmerge"] line. Then I'm setting the tool "diffmerge" as the default in the [diff] tool = section.

I obviously have the "diffmerge" command in my path, here. Otherwise I'd need to give a full path to the executable.

Adding one of the blocks below works for me to use KDiff3 for my Windows and Linux development environments. It makes for a nice consistent cross-platform diff and merge tool.

Linux

[difftool "kdiff3"]
    path = /usr/bin/kdiff3
    trustExitCode = false
[difftool]
    prompt = false
[diff]
    tool = kdiff3
[mergetool "kdiff3"]
    path = /usr/bin/kdiff3
    trustExitCode = false
[mergetool]
    keepBackup = false
[merge]
    tool = kdiff3

Windows

[difftool "kdiff3"]
    path = C:/Progra~1/KDiff3/kdiff3.exe
    trustExitCode = false
[difftool]
    prompt = false
[diff]
    tool = kdiff3
[mergetool "kdiff3"]
    path = C:/Progra~1/KDiff3/kdiff3.exe
    trustExitCode = false
[mergetool]
    keepBackup = false
[merge]
    tool = kdiff3

If you want to have an option to use multiple diff tools, add an alias to file .gitconfig:

[alias]
    kdiff = difftool --tool kdiff3

Refer to Microsoft's VS Code Tips and Tricks. Just run these commands in your terminal:

git config --global merge.tool code

But firstly you need add the code command to your PATH environment variable.

In Windows we need to run the git difftool --tool-help command to see the various options like:

    'git difftool --tool=<tool>' may be set to one of the following:
                    vimdiff
                    vimdiff2
                    vimdiff3

    The following tools are valid, but not currently available:
                    araxis
                    bc
                    bc3
                    codecompare
                    deltawalker
                    diffmerge
                    diffuse
                    ecmerge
                    emerge
                    examdiff
                    gvimdiff
                    gvimdiff2
                    gvimdiff3
                    kdiff3
                    kompare
                    meld
                    opendiff
                    p4merge
                    tkdiff
                    winmerge
                    xxdiff

Some of the tools listed above only work in a windowed
environment. If run in a terminal-only session, they will fail.

And we can add any of them (for example, WinMerge) like

git difftool --tool=winmerge

For configuring Notepad++ to see files before committing:

 git config --global core.editor "'C:/Program Files/Notepad++/notepad++.exe' -multiInst -notabbar -nosession -noPlugin"

And using git commit will open the commit information in Notepad++.

Almost all the solutions in the previous answers doesn't work with Git version 2

Mine: Git version = 2.28.0

Solution of the difftool: git config --global diff.tool vimdiff

After it, you can use it without any problems.