Git doesn't support "orange"; use "yellow".

6e6508408b7ee7e595d657bba0fc30de076fae4c set the default colour for modified
files to:

    git config --get-color "gitsh.color.modified" "orange"

Unfortunately, there is no "orange". The colour has always been called
"yellow", it just looks orange in preferred terminal emulator colour scheme.

Oops.
Commit the generated INSTALL documentation

The `INSTALL` file is generated from `INSTALL.in`; however, since it is
the installation guide, it is often read before the program is even
downloaded. For example, on GitHub we link to `INSTALL.in` from the
`README.md`. Rather than recommend that people read a template of a
documentation, we can instead simply add the generated documentation to
the repo.