Why can't I use TortoiseMerge as my git merge tool on Windows?

Question

I'm trying to perform my first Git merge ever (exciting!), but can't get Git Gui (0.13.GITGUI from Git 1.7.4.msysgit.0) to recognize TortoiseMerge (1.6.11.20210 x64) on Windows 7. Based on an answer to a similar question, I've made the following configuration changes:

$ git config --global merge.tool tortoisemerge
$ git config --global mergetool.tortoisemerge.cmd 'TortoiseMerge.exe -base:"$BASE" -mine:"$LOCAL" -theirs:"$REMOTE" -merged:"$MERGED"'
$ git config --global --list
...snip...
merge.tool=tortoisemerge
mergetool.tortoisemerge.cmd=TortoiseMerge.exe -base:"$BASE" -mine:"$LOCAL" -theirs:"$REMOTE" -merged:"$MERGED"
$

Unfortunately, when I start Git Gui and attempt to "Run Merge Tool", I receive the error Unsupported merge tool 'tortoisemerge'.

Can anyone tell me what I've done wrong? Here's the relevant sections of my ~/.gitconfig:

[merge]
        tool = tortoisemerge
[mergetool "tortoisemerge"]
        cmd = TortoiseMerge.exe -base:\"$BASE\" -mine:\"$LOCAL\" -theirs:\"$REMOTE\" -merged:\"$MERGED\"

Update

TortoiseMerge works fine with the above config when running git mergetool from the command line. It seems that only Git Gui has problems with it. :-/

Answer 1

If you have the latest git, run this command line once:

git config merge.tool tortoisemerge

Important: Do not add a .exe extension to the command.

If that fails, or if you want to add a different merge tool that git doesn't know about, do this:

Open one of the following in an editor:

• 64-bit git: C:\Program Files\Git\mingw64\share\git-gui\lib\mergetool.tcl
• 32-bit git: C:\Program Files (x86)\Git\share\git-gui\lib\mergetool.tcl

Add something like this to mergetool.tcl:

tortoisemerge {
    set cmdline [list TortoiseMerge.exe -base:"$BASE" -mine:"$LOCAL" -theirs:"$REMOTE" -merged:"$MERGED"]
}

Put the new tortoisemerge entry above this other code:

default {
        error_popup [mc "Unsupported merge tool '%s'" $tool]
        return
}

Bonus example:

To use SourceGear diffmerge, add this to mergetool.tcl:

diffmerge {
    set cmdline [list "C:/Program Files (x86)/SourceGear/DiffMerge/DiffMerge.exe" --merge --result=$MERGED $LOCAL $BASE $REMOTE]
}