The command without arguments already prints all installed distributions
found.

In addition, change “releases” for “projects” in the description of the
list action.  Strictly speaking, one installed distribution satisfies
the requirement for a release (i.e. version) of a project, but as
currently only one release per project can be installed at a time, the
two are somewhat equivalent, and “project” is more understandable in
help texts (which call their argument “dist”, by the way..)

While we're at it, also document ZLIB_VERSION.

Patch by Torsten Landschoff.

instead of ignoring it and always using a compression level of 9.

Thanks July Tikhonov.

This is copied from the namesake distutils command; there is no
automated test, so buildbots won’t call for my head this time, but it
should be okay as Python 3 users have tested the distutils command.

In dry-run mode, packaging commands should log the same info as in real
operation and should collect the same files in self.outputs, so that
users can run a command in verbose and dry-run mode to see exactly what
operations will be done in the real run.

Original patch by Filip Gruszczyński.

New tests were added in test_metadata and old tests inherited from
distutils were still in test_dist, so I moved them into test_metadata
(except for one which was more at home in test_run) and merged
duplicates.

I also added some skips to lure contributors <wink>, optimized the
Metadata.update method a trifle, and added notes about a number of
issues.

A note: The tests in test_dist used to dump the Metadata objects to a
file in the METADATA format and look for strings in its contents; I
updated them to use the mapping API of Metadata instead.  For some
fields with special writing rules, I have added tests to ensure my
conversion did not lose anything.

I have tests to add in this file and it’s always nice to start from a
clean base.

Also fix some markup and typos.

atime and mtime with nanosecond precision on modern POSIX platforms.

configure.in: Set _POSIX_C_SOURCE to 200809L, instead of 200112L, to activate
features from IEEE Stds 1003.1-2008.

configure: Set _XOPEN_SOURCE to 700, instead of 600, to get POSIX 2008
functions on OpenBSD (e.g. fdopendir).

PyLong_AsDouble() and PyLong_AsUnsignedLongLong() now raise TypeError (rather
than SystemError) when passed a non-integer argument, matching the behavior of
all the other PyLong_As*() functions.