hgweb: query string arguments to control whitespace for annotate This feature should hopefully be pretty straightforward. We simply examine some query string arguments to feed into the diff options. The function to obtain the diff options has been factored into its own generic function to facilitate an upcoming change to the HTML interface and to enable diff settings to be controlled via the same query string arguments on other web commands. The test output for "ignoreblanklines" didn't change. I'm not sure why. Our test coverage for --ignore-blank-lines isn't great and I can't figure out how to make this diff setting do anything meaningful. On a very brief examination of the code, it is possible the setting doesn't work because it is operating at the line level and blank lines detection needs to examine multiple lines. But I'm not an expert in this code, so I'm not sure. Differential Revision: https://phab.mercurial-scm.org/D849