hgweb: filter diff hunks when 'linerange' and 'patch' are specified in filelog

hgweb: add a 'linerange' parameter to webutil.diffs() This is used to filter out hunks based on their range (with respect to 'node2' for patch.diffhunks() call, i.e. 'ctx' for webutil.diffs()). This is the simplest way to filter diff hunks, here done on server side. Later on, it might be interesting to perform this filtering on client side and expose a "toggle" action to alternate between full and filtered diff.

hgweb: handle a "linerange" request parameter in filelog command We now handle a "linerange" URL query parameter to filter filelog using a logic similar to followlines() revset. The URL syntax is: log/<rev>/<file>?linerange=<fromline>:<toline> As a result, filelog entries only consists of revision changing specified line range. The linerange information is propagated to "more"/"less" navigation links but not to numeric navigation links as this would apparently require a dedicated "revnav" class. Only update the "paper" template in this patch.

shelve: add logic to preserve active bookmarks This adds an explicit active-bookmark-handling logic to shelve. Traditional shelve handles it by transaction aborts, but it is a bit ugly and having an explicit functionality seems better.

metadataonlyctx: speed up sanity check Previously the sanity check will construct manifestctx for both p1 and p2. But it only needs the "manifest node" information, which could be read from changelog directly.

revset: factor out linerange processing into a utility function Similar processing will be done in hgweb.webutil in forthcoming changeset.

hgweb: add a "patch" query parameter to filelog command Add support for a "patch" query parameter in filelog web command similar to --patch option of `hg log` to display the diff of each changeset in the table of revisions. The diff text is displayed in a dedicated row of the table that follows the existing one for each entry and spans over all columns. Only update "paper" template in this patch.

hgweb: handle "parity" internally in webutil.diffs() There's apparently no reason to have the "parity" of diff blocks that webutil.diffs() generates coming from outside the function. So have it internally managed. We thus now pass a "web" object to webutil.diffs() to get access to both "repo" and "stripecount" attribute.