This is a standalone envdir-like utility -- it lets you read the first lines of files in a directory into corresponding environment variables.
For example, if you run
denv confdir progname --other-args
where confdir is a directory containing these files
$ cat confdir/FOO
peanut butter
$ cat confdir/BAR
sriracha
$ cat confdir/BAZ # where BAZ is executable
#!/bin/sh
echo "garlic"
then progname will be run with an environment like
env FOO="peanut butter" BAR="sriracha" BAZ="garlic" progname --other-args
If a file exists but is empty, then the variable will be cleared. Executable files yield their first line of output.
(If you find this useful, you might also want to check out skel.)
While I highly recommend daemontools (or runit, etc.), there's no reason this handy little tool should depend on it.