contrib: drop old convert-repo script

This has been obsolete since 2007.
contrib: drop obsolete sample.hgrc

This was full of bad suggestions and is obsoleted by hg config --edit.
build: don't use -s flag for `which`

`which -s` is a BSDism that doesn't exist on other versions of
`which`. That means that even on Mac OS X, `make osx` breaks if you have
another utils package installed (e.g. debianutils installed thru
fink). Redirect output to /dev/null instead.
obsolete: avoid slow, generic date parsing

Simple profiling of `hg log -r .` revealed ~18,000 calls to
mercurial.i18n.gettext() on the author's repository. The
culprit was 3 _() calls in util.parsedate() multiplied by
~6000 obsmarkers originating from the parsing of obsmarkers.

Changing the obsmarker code to parse the stored format of
dates instead of going through a generic path eliminates these
gettext() lookups and makes `hg log -r .` execute ~10% faster
on the author's repo. The performance gain is proportional to
the number of obsmarkers.

The author attempted to patch util.parsedate() to avoid the
gettext() lookups. However, that code is whacky and the author
is jet lagged, so the approach was not attempted.
debugdag: stop wrongly sorting parents

The dag being dumped is not in a format that allows us to reconstruct the
original dag as the parent revisions are normalised.
debugrevlog: add chainlen column to --dump output
revsetbenchmark: add revset with lazyset subtraction

The added revset is used by obsolescence and currently results in
recursion in __contains__ between 2 lazysets. We should have
coverage of this revset.
memctx: allow extensions to determine what filectxfn should do

Rev 650b5b6e75ed switched the contract for filectxfn from "raise IOError if
file is missing" to "return None if file is missing". Out of tree extensions
need to be updated for that, but for extensions interested in compatibility
with both Mercurial <= 3.1 and default, it is next to impossible to introspect
core Mercurial to figure out what to do.

This patch adds a field to memctx for extensions to use.
bookmarks: refer to "the" active bookmark to clarify that there's only one

This is a follow-on to 0c6cdbb697d9 that just makes a slight clarification.

--HG--
branch : stable
merge with crew