logging: add special logging level "KEEP"

Without this, the user cannot configure only certain logging domains
without touching them all.

E.g.

  # nmcli general logging level DEBUG domains PLATFORM

will disable all non-PLATFORM domains.
Well, the user can do:

  # nmcli general logging level INFO domains PLATFORM:DEBUG
  # nmcli general logging level DEBUG domains ALL:INFO,PLATFORM

but in this case all non-PLATFORM domains are reset explicitly.

Now the user can:

  # nmcli general logging level KEEP domains PLATFORM:DEBUG
  # nmcli general logging level DEBUG domains ALL:KEEP,PLATFORM

which will only change the platform domain.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/nm-logging.h b/src/nm-logging.h
index db9f0b1557..b54078186e 100644
--- a/src/nm-logging.h
+++ b/src/nm-logging.h
@@ -94,6 +94,7 @@ typedef enum  { /*< skip >*/
 	_LOGL_N_REAL, /* the number of actual logging levels */
 
 	_LOGL_OFF = _LOGL_N_REAL, /* special logging level that is always disabled. */
+	_LOGL_KEEP,               /* special logging level to indicate that the logging level should not be changed. */
 
 	_LOGL_N, /* the number of logging levels including "OFF" */
 } NMLogLevel;