env: make "env default" selective, check and apply

Change the syntax (user API) for "env default":
  -f: override write-once variables
  var... : accept individual variable(s)
  -a: all (resetting the whole env is NOT the default behavior)

Enable variable checking and make changes effective by
enabling do_apply argument to himport_r().

Signed-off-by: Gerlando Falauto <gerlando.falauto@keymile.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/environment.h b/include/environment.h
index 90fb1302b1..e8ab7033bf 100644
--- a/include/environment.h
+++ b/include/environment.h
@@ -181,6 +181,9 @@ void env_crc_update(void);
 /* [re]set to the default environment */
 void set_default_env(const char *s);
 
+/* [re]set individual variables to their value in the default environment */
+int set_default_vars(int nvars, char * const vars[]);
+
 /* Import from binary representation into hash table */
 int env_import(const char *buf, int check);