addremove: add labels for messages about added and removed files This is the first step to add color for add and remove output.

revlog: filter out "invalid" delta base candidates There are bases that we know won't produce a good delta chain. For example, if the base is already bigger than twice the size of the text we store, we know the resulting delta chain will never be valid. We might make the check a bit more powerful and generic in the future, but this looks a good start. In particular, empty file (size 0) will never find a good base, so we should stop spending time trying to find one.

revlog: use a symbolic constant for the deltas/text ration We are about to use it somewhere else, we should as well make it easier to access and change.

revlog: do not search for delta for empty content We won't find any useful base to store an empty text. So we should not even try to.

revlog: split and document good delta conditional The logic is still identical, but having each conditional on its own helps to document them and will help to edit them in the future.

revlog: skip over empty revision when looking for delta base There is no point in keeping an empty revision in the middle of a chain since they won't contribute any data. So we filter them out when looking for a valid base delta.

debugrevlog: display details about empty revision We now display details about the course of emptiness (empty text or empty delta).

debugrevlog: track empty revlog entries A revlog entry can be "empty" for two reasons: * the stored text is empty * we found another entry with the exact same content Tracking them separately make revlog content clearer.

debugrevlog: document some of the variable used This help to understand the code.

revlog: drop compatibility for `revlog.descendant` (API) As advertised, the method is dropped in 4.8.

context: drop compatibility for `context.descendant` (API) As advertised, the method is dropped in 4.8.

cmdutil: remove _updatecleanmsg() which is no longer used anywhere

cmdutil: fix weird indent in _mergemsg()

cext: fix a warning about differing const qualifiers on Windows The prototype takes a 'void *', but self->offsets is a 'const char **'. mercurial/cext/revlog.c(2011) : warning C4090: 'function' : different 'const' qualifiers

cext: fix most truncation warnings in revlog on Windows There's one more, and I'm not sure why it isn't being tripped on other platforms: mercurial/cext/revlog.c(430) : warning C4244: '=' : conversion from 'Py_ssize_t' to 'char', possible loss of data

cext: fix Windows warning about implicit conversion of 32-bit shift to 64 bit mercurial/cext/revlog.c(1541) : warning C4334: '<<' : result of 32-bit shift implicitly converted to 64 bits (was 64-bit shift int ended?)