add option to ignore log entries

[rladstaetter]

It would be handy if there was a context menu for the log text display which allows to ignore all entries prior or following the current selection. if one searches for a certain event then one is only interested in a certain time span - with such an option it would be easy to just throw away uninteresting parts of the log file.

For example, this could be implemented with two options in the context menu:

• ignore all prior log entries
• ignore all log entries following the current log entry

To keep things simple, this option should just look at the index of the given log entry and apply operations accordingly. Active filters should not have any impact. Also, if the 'follow' mode should not be affected by this option.

The context menu should look something like this:

It is not necessary that this option is persistent - that means that those settings are reset if a filter change was applied or the file was reloaded. This could be fixed in the future if it turns out to be necessary.