Setup p4merge as difftool and mergetool on Windows

p4merge-git-tool.md

Setting up p4merge as diff and merge tool on Windows. Tried for Git version 1.8.4.msysgit.0.

Two alternatives are explained: using the command line, and directly editing the config file.

Setting up from the command line

Being the installation path "C:Program Files\Perforce\p4merge.exe", just run:

$ git config --global diff.tool p4merge
$ git config --global difftool.p4merge.path 'C:\Program Files\Perforce\p4merge.exe'

$ git config --global merge.tool p4merge
$ git config --global mergetool.p4merge.path 'C:\Program Files\Perforce\p4merge.exe'

Possible error if other approaches have been tried before

Apparently in earlier versions mergetool.p4merge.cmd needed to be provided instead of the path, but doesn't work anymore due to Git trying to support p4merge:

setting mergetool.p4merge.cmd will not work anymore since Git has started trying to support p4merge, see libexec/git-core/git-mergetool--lib. instead it directly uses mergetool.p4merge.path

If that option is already set (check if git config --global --get mergetool.p4merge.cmd prints a value), it needs to be removed:

$ git config --global --unset mergetool.p4merge.cmd

The same applies to difftool.p4merge.cmd.

Editing the global configuration file

Open ~/.gitconfig (git config --global --edit) and add or change:

[merge]
	tool = p4merge
[mergetool "p4merge"]
	path = C:\\Program Files\\Perforce\\p4merge.exe

[diff]
	tool = p4merge
[difftool "p4merge"]
	path = C:\\Program Files\\Perforce\\p4merge.exe

As before, if inside [mergetool "p4merge"] or [difftool "p4merge"] there is a cmd option, it needs to be removed so that Git doesn't try to execute it.