bash - Set environment variables from file of key/value pairs

I have upvoted user4040650's answer because it's both simple, and it allows comments in the file (i.e. lines starting with #), which is highly desirable for me, as comments explaining the variables can be added. Just rewriting in the context of the original question.

If the script is callled as indicated: minientrega.sh prac1, then minientrega.sh could have:

set -a # export all variables created next
source $1
set +a # stop exporting
# test that it works
echo "Ficheros: $MINIENTREGA_FICHEROS"

The following was extracted from the set documentation:

This builtin is so complicated that it deserves its own section. set
allows you to change the values of shell options and set the
positional parameters, or to display the names and values of shell
variables.

set [--abefhkmnptuvxBCEHPT] [-o option-name] [argument …] set
[+abefhkmnptuvxBCEHPT] [+o option-name] [argument …]

If no options or arguments are supplied, set displays the names and values of all shell
variables and functions, sorted according to the current locale, in a
format that may be reused as input for setting or resetting the
currently-set variables. Read-only variables cannot be reset. In POSIX
mode, only shell variables are listed.

When options are supplied, they set or unset shell attributes.
Options, if specified, have the following meanings:

-a Each variable or function that is created or modified is given the export attribute and marked for export to the environment of
subsequent commands.

And this as well:

Using ‘+’ rather than ‘-’ causes these options to be turned off. The
options can also be used upon invocation of the shell. The current set
of options may be found in $-.