Nested Fossil Repositories

The usecase driving fossil's ability to nest the checkout of one repository into the checkout of another was that we (the Tcl Maintainers) wanted to share the same tclconfig/ across many packages instead of maintaining actual copies per package.

A concrete example of this can be found at Tracking Thread Sources with tclconfig nested into a checkout of package Thread.

Generalized the setup looks like shown below, with the package INNER nested into the checkout of OUTER.

# Start with a regular checkout of a project OUTER

% mkdir outer
% cd outer
% fossil open /path/to/outer.fossil

# Then add the INNER project
# Remember, we are in .../outer here

% mkdir inner
% cd inner
% fossil open --nested /path/to/inner.fossil

# Note the --nested option in the last command. This is necessary to make this work.