This is not a command the end user would want to run. Ever.
This documentation is meant for people who are studying the
Porcelain-ish scripts and/or are writing new ones.
The git-mergetool--lib scriptlet is designed to be sourced (using
.) by other shell scripts to set up functions for working
with Git merge tools.
Before sourcing git-mergetool--lib, your script must set TOOL_MODE
to define the operation mode for the functions listed below.
diff and merge are valid values.