add MKSH_ENVDIR code for Jehanne (OS by Shamar (giacomotesio) from IRC):

instead of parsing extern char **environ; read it from a filesystem
(typical for Plan 9, though this one is __jehanne__ per ifdef)

tested on MirBSD and found to be working

main.c

@@ -34,9 +34,7 @@
#include <locale.h>
#endif

__RCSID("$MirOS: src/bin/mksh/main.c,v 1.344 2017/10/13 23:02:11 tg Exp $");

extern char **environ;
__RCSID("$MirOS: src/bin/mksh/main.c,v 1.345 2017/10/14 21:05:22 tg Exp $");

#ifndef MKSHRC_PATH
#define MKSHRC_PATH	"~/.mkshrc"
@@ -52,6 +50,7 @@ void chvt_reinit(void);
static void reclaim(void);
static void remove_temps(struct temp *);
static mksh_uari_t rndsetup(void);
static void init_environ(void);
#ifdef SIGWINCH
static void x_sigwinch(int);
#endif
@@ -397,14 +396,7 @@ main_init(int argc, const char *argv[], Source **sp, struct block **lp)
#endif

	/* import environment */
	if (environ != NULL) {
		wp = (const char **)environ;
		while (*wp != NULL) {
			rndpush(*wp);
			typeset(*wp, IMPORT | EXPORT, 0, 0, 0);
			++wp;
		}
	}
	init_environ();

	/* for security */
	typeset(TinitIFS, 0, 0, 0, 0);
@@ -1976,3 +1968,84 @@ x_mkraw(int fd, mksh_ttyst *ocb, bool forread)

	mksh_tcset(fd, &cb);
}

#ifdef MKSH_ENVDIR
static void
init_environ(void)
{
	char *xp;
	ssize_t n;
	XString xs;
	struct shf *shf;
	DIR *dirp;
	struct dirent *dent;

	if ((dirp = opendir(MKSH_ENVDIR)) == NULL) {
		warningf(false, "cannot read environment from %s: %s",
		    MKSH_ENVDIR, cstrerror(errno));
		return;
	}
	XinitN(xs, 256, ATEMP);
 read_envfile:
	errno = 0;
	if ((dent = readdir(dirp)) != NULL) {
		if (skip_varname(dent->d_name, true)[0] == '\0') {
			xp = shf_smprintf(Tf_sSs, MKSH_ENVDIR, dent->d_name);
			if (!(shf = shf_open(xp, O_RDONLY, 0, 0))) {
				warningf(false,
				    "cannot read environment %s from %s: %s",
				    dent->d_name, MKSH_ENVDIR,
				    cstrerror(errno));
				goto read_envfile;
			}
			afree(xp, ATEMP);
			n = strlen(dent->d_name);
			xp = Xstring(xs, xp);
			XcheckN(xs, xp, n + 32);
			memcpy(xp, dent->d_name, n);
			xp += n;
			*xp++ = '=';
			while ((n = shf_read(xp, Xnleft(xs, xp), shf)) > 0) {
				xp += n;
				if (Xnleft(xs, xp) <= 0)
					XcheckN(xs, xp, Xlength(xs, xp));
			}
			if (n < 0) {
				warningf(false,
				    "cannot read environment %s from %s: %s",
				    dent->d_name, MKSH_ENVDIR,
				    cstrerror(shf_errno(shf)));
			} else {
				*xp = '\0';
				xp = Xstring(xs, xp);
				rndpush(xp);
				typeset(xp, IMPORT | EXPORT, 0, 0, 0);
			}
			shf_close(shf);
		}
		goto read_envfile;
	} else if (errno)
		warningf(false, "cannot read environment from %s: %s",
		    MKSH_ENVDIR, cstrerror(errno));
	closedir(dirp);
	Xfree(xs, xp);
}
#else
extern char **environ;

static void
init_environ(void)
{
	const char **wp;

	if (environ == NULL)
		return;

	wp = (const char **)environ;
	while (*wp != NULL) {
		rndpush(*wp);
		typeset(*wp, IMPORT | EXPORT, 0, 0, 0);
		++wp;
	}
}
#endif