revlog: reset _nodepos after strip When using the pure revlog parser, _nodepos is used to keep track of the position during index scanning in the non-cached cache. If it is out of bounds, BaseIndexObject._fix_index will assert. Since strip can actually remove the position scanned last, make sure to reset it. Add an assertion in the place where the invariance is clearer. Differential Revision: https://phab.mercurial-scm.org/D3188

paper: make all source lines have the same minimum height Empty source lines in paper and coal themes used to have smaller height than every other line (because of the way line numbers are shown and because they are using smaller font). This wasn't very noticeable before the follow lines functionality was added, but after that just using the follow-lines button to select a block of code with empty lines would demonstrate the fact that empty lines didn't have enough height - there were white "gaps" in the selection block. Since this problem occurs when lines don't have any content inside, let's create a pseudo-element (it's unselectable because of that) which still doesn't have any content, but fills up empty lines to 100% of their height because of display: inline-block. This is the most natural way to solve this annoyance that I've found so far. Hardcoding height isn't useful because we can have wrapped lines, in which case multiple lines of text need to fit into a single <span>. Setting min-height or line-height doesn't remove the gaps when viewed in Chromium.

hgweb: make followlines button absolutely positioned It used to have position: absolute only on annotate page, but it makes sense to have it everywhere, because the button shouldn't affect other elements at all. Especially since the button has a set height, which meant that for certain smaller fonts source lines were changing their height on hover. Note that the button doesn't set any of the usual properties that accompany absolute position (top, right, bottom or left). These properties would position the button without any account for source line padding. Instead, margins are used (the button already has all margins defined, they do the job).

hgweb: insert followlines buttons before any children, including text nodes This way the buttons come before any other content, including text nodes. Because highlight extension replaces every line of text with some <span> elements that have CSS classes for highlighting, the placement of followlines buttons used to depend on if that extension was enabled or not. Let's make the placement more consistent, it'll help the next patch in this series.