Custom mergetool cmd support in git GUI

[elecpic]

git GUI doesn't actually support custom mergetool cmd when providing the following .gitconfig:

[merge]
tool = mymerge
[mergetool]
cmd = mymerge "$BASE" "$LOCAL" "$REMOTE" -o "$MERGED"

Instead git-gui popups the error: "Unsupported merge tool 'mymerge'"

This post: http://stackoverflow.com/a/15984079 directed me to Git/share/git-gui/lib/mergetool.tcl where I fixed the issue in a way to support custom cmd specified in .gitconfig. At least, it works for me...

Here's the file (I didn't find where to attach other than image files):

[dscho]

Please fork & clone https://github.com/msysgit/git, patch the problem, provide a proper commit message with sign-off and open a Pull Request.