Use PHPStorm/WebStorm for git diff and merge tools

.gitconfig

# ~/.gitconfig
# Add this to your global git configuration file
# Change pstorm to wstorm, if you use that.

# Diff and merge tool changes
# Run `git difftool <directory/file>...` or `git mergetool <directory/file>...`
[diff]
  tool = pstorm
[difftool]
  prompt = false
[difftool.pstorm]
  cmd = /usr/local/bin/pstorm diff "$LOCAL" "$REMOTE"
[merge]
  tool = pstorm
[mergetool.pstorm]
  cmd = /usr/local/bin/pstorm merge "$LOCAL" "$REMOTE" "$BASE" "$MERGED"