Merge with stable (5.5)

.hgignore

.hgsigs

.hgtags

contrib/chg/chg.c

contrib/dumprevlog

contrib/fuzz/Makefile

contrib/fuzz/manifest.cc

contrib/fuzz/manifest_corpus.py

contrib/fuzz/pyutil.cc

contrib/heptapod-ci.yml

contrib/packaging/debian/rules

contrib/perf.py

contrib/simplemerge

contrib/undumprevlog

hgdemandimport/__init__.py

hgext/absorb.py

hgext/clonebundles.py

hgext/convert/cvs.py

hgext/convert/gnuarch.py

hgext/convert/monotone.py