extensions: allow extending command synopsis and docstring Mercurial uses a synopsis string and the docstring of a command for the command's help output. Today there is no way for an extension that adds functionality to a command to extend either of these help strings. This patch enables appending to both the doctring and the synopsis, and adds a test for this functionality. Example usage is shown in the test and is also described in the docstring of extensions.wrapcommand().

revlog: _addrevision creates full-replace deltas based on censored revisions A delta against a censored revision is either received through exchange and written blindly to a revlog, or it is created by the revlog itself. This change ensures the latter process creates deltas which fully replace all data in a censored base using a single patch operation. Recipients of a delta against a censored base will verify that the delta is in this full-replace format. Other recipients will use the delta as normal. For background and broader design of the censorship feature, see: http://mercurial.selenic.com/wiki/CensorPlan

revlog: special case expanding full-replacement deltas received by exchange When a delta received through exchange is added to a revlog, it will very often be expanded to a full text by applying the delta to its base. If that delta is of a particular form, we can avoid decoding the base revision. This avoids an exception if the base revision is censored. For background and broader design of the censorship feature, see: http://mercurial.selenic.com/wiki/CensorPlan

test-merge-tools: fix flaky test by avoiding debugsetparents debugsetparents is a debug command and does not provide the same guarantees as non-debug commands do. In particular, when the user sets a different parent, any clean files will remain clean in the dirstate even though the new parent might have a different version of the file (so it should appear modified compared to the new parent). Let's instead achieve the same effect by updating to the new parent and reverting the contents back to what they were. This fix can be tested by passing '--config debug.dirstate.delaywrite=2' to the 'hg update' command in the beforemerge().