add a flag to specify which *master files to use

This prepares a new option like --ignore-emaster.

Signed-off-by: Ruediger Meier <ruediger.meier@ga-group.nl>
add option to ignore certain master files

Signed-off-by: Ruediger Meier <ruediger.meier@ga-group.nl>
don't complain about missing but unwanted master files

Signed-off-by: Ruediger Meier <ruediger.meier@ga-group.nl>
fix, don't try to dump non-existing or unwanted masters

Signed-off-by: Ruediger Meier <ruediger.meier@ga-group.nl>
remove unsused function hasXMaster()

Signed-off-by: Ruediger Meier <ruediger.meier@ga-group.nl>
fix, handle inconsistent EMASTER file

Reported-by: Valentino Botta <valentino.botta@gmail.com>
Signed-off-by: Ruediger Meier <ruediger.meier@ga-group.nl>
don't abort on missing data files

Signed-off-by: Ruediger Meier <ruediger.meier@ga-group.nl>
Merge branch 'ignore-masters'

* ignore-masters:
  don't abort on missing data files
  fix, handle inconsistent EMASTER file
  remove unsused function hasXMaster()
  fix, don't try to dump non-existing or unwanted masters
  don't complain about missing but unwanted master files
  add option to ignore certain master files
  add a flag to specify which *master files to use