This brings this control in line with other diagnostic controls we have which operate on a per-group level.
'DefaultIgnoreWarnings' diagnostic group option applies to all warnings belonging to a certain diagnostic group.
The inheritance rules are:
- Marking a diagnostic group as 'DefaultIgnoreWarnings' means warnings belonging to this group will not be emitted by-default
- Warnings belonging to sub-groups of this group will also not be emitted by-default
- Enabling a 'DefaultIgnoreWarnings' group (with '-Werror','-Wwarning', etc.) means warnings belonging to this group will be emitted.
- Warnings belonging to sub-groups of this group will also be emitted.
- Warnings belonging to super-groups of this group will not be affected.
The serialized diagnostic format has some extra fields that we can
adopt for diagnostic groups. Specifically:
* Category: store the diagnostic group name here
* Flags: extend the hack used by educational notes of placing Markdown file paths here
The inclusion of the full diagnostic list (via DiagnosticList.h) in
DiagnosticGroups.h meant that touching any diagnostic caused most of
the world to rebuild, making me sad. Use forward declarations to limit
how much needs to be rebuilt when changing diagnostics.
This commit adds new compiler options -no-warning-as-error/-warning-as-error which allows users to specify behavior for exact warnings and warning groups.
