* geesh/shell.scm (%subshell): New function factored out from 'subshell'.
(subshell): Use it.
(substitute-command): New public function.
* tests/shell.scm: Test it.
* .dir-locals.el: Indent it nicely.
* geesh/shell.scm (save-and-install-redirect!): New function.
(restore-saved-fdes!): New function.
(with-redirects): New public function.
* tests/shell.scm: Test it.
* .dir-locals.el: Indent it nicely.
* geesh/built-ins/echo.scm: New file.
* geesh/built-ins.scm: New file.
* Makefile.scm: Add them.
* geesh/shell.scm (exec-let): Include built-ins in command search.
* tests/shell.scm: Add a test for this.
* geesh/shell.scm (slashless?) New function.
(split-search-path): New function.
(find-utility): New function.
(exec-let): Use them to search PATH for a utility when appropriate.
(exec): Update doc string.
* tests/shell.scm: Test it.
Timothy Sample