CVS rlog for a given module sent by server is a concatenation of
rlog entries. Each entry has a header containing the path to a
RCS file plus other info.

It exist cases where a rlog entry header is empty which makes the
rlog parsing fail.

So instead of stopping rlog parsing by raising an exception, prefer
to skip that entry and process the next one.

Closes T4629

Instead of using the readlines method on file objects that retrieve all
lines of a file and store them in memory, prefer to read files line
by line by using the lazy generator of lines from file objects.

This significantly reduce loader memory consumption when processing
a large rlog output stored in a file.

That case was handled when using rsync protocol but not when using pserver
or ssh protocol.

Closes T4631

When attempting to fetch the rlog for a path that does not exist in
the repository, the CVS server will respond with the following lines:

E cvs rlog: could not read RCS file for <path>
ok

That error case was not handled in fetch_rlog so ensure it returns None
when encountering it.

The issue was spotted when the loader attempts to fetch more rlog data from
Attic directories. The paths of these Attic directories are computed from
those of the files in the repositories but it exist cases where those
directories do not exist.

Since Python 3.10, support for PyArg_ParseTuple() # formats
requires PY_SSIZE_T_CLEAN macro to be defined.

It exists CVS respositories where revision numbers greather than 1.x
are used to version files.

Previous loader implementation was raising an error when encountering
such kind of revision so ensure it will be processed as the other ones.

Also fix tag names extraction from rlog output.

Related to T4043

It exists cases where rsync output will not be ascii decodable so prefer
to use utf-8 instead.

It makes the loading process fail otherwise.

Some CVS repositories have paths which are non valid UTF-8 (typically
ISO-8859-1 ones) but the loader implementation assumed all paths can
be safely encoded to UTF-8 and was raising UnicodeEncodeError when
attempting to encode non UTF-8 paths.

That commit modifies the way CVS paths are handled by the loader by
using their raw bytes representation instead of their UTF-8 decoded
string representation.

Also rcsparse.rcsfile constructor has been modified to take bytes path
as argument instead of an unicode one in order to be able to successfully
open non UTF-8 paths.

Such CVS repositories can now be successfully loaded, either using rsync
or pserver protocol.

Related to T3980

Connection to an existing pserver might sometimes fail (on SourceForge
for instance), retrying the operation usally fixes the issue.

Some CVS servers (SourceForge and OSDN for instance) return an error if
the path sent with the "Directory" pserver request is not absolute.

So fix that issue to ensure loading of such CVS repositories.

The CVS client was raising an error when trying to connect to such pserver
URL: pserver://anonymous@cvs.example.org/cvsroot/project/module

But numerous CVS pserver URLs that can be found in the wild (notably on
SourceForge and OSDN) are in that form.

So add support for such URL form in the CVS client.

Also remove use of external dependency urllib3.util.parse_url and prefer
to use urllib.parse.urlparse from standard Python library.

A change in the base loader will allow to increase it punctually if needed in debugging
mode.

Recent changes in swh-scheduler add new parameters to the celery tasks
produced from swh.scheduler.model.ListedOrigin instances.

So ensure to handle any new parameters by not hardcoding the expected
ones in task signatures.

Remove unsafe use of unnamed task parameters.

Add new tests checking task parameters produced from ListedOrigin
instances do no raise error when attempting to create a cvs loader.

Related to T4187

9474ab23 was a workaround for this role being
unknown to PyPI.

Removing the role fixes the issue. I also do not think it is very useful;
all loaders have this entry point.

Otherwise, the upload-to-pypi build complains about it [1]

[1] https://jenkins.softwareheritage.org/job/DLDCVS/job/pypi-upload/12/console

That hook can be frustrating as it can discard a long commit message
if it finds a typo in it so better removing it.

Fetching CVS repository data using rsync often fails with the following error
(especially with archived repositories hosted on sourceforge):

rsync error: some files/attrs were not transferred (see previous errors) (code 23)

It seems the only way to mitigate that issue is to retry the rsync command
until it succeeds.

So add a rsync_retry decorator and apply it to a new method in the loader
wrapping the call to subprocess.run executing the rsync command.

Also use rsync option to compress file data during the transfer.

Related to T3922

black is considered stable since release 22.1.0 and the version
we are currently using is quite outdated and not compatible with
click 8.1.0, so it is time to bump it to its latest stable release.

Please note that E501 pycodestyle warning related to line length
is replaced by B950 one from flake8-bugbear as recommended by black.
https://black.readthedocs.io/en/stable/the_black_code_style/current_style.html#line-length

Related to T3922

pytest-postgresql 3.1.3 and pytest-redis 2.4.0 added support for
pytest >= 7 so we can now drop the pytest pinning.

Due to test modules being copied in subdirectories of the
build directory by setuptools, it makes pytest fail by raising
ImportPathMismatchError exceptions when invoked from root
directory of the module.

So ignore the build folder to discover tests.

And use f-string when raising

To install the new hook:

  $ pre-commit install -t commit-msg

Related to T3916

Related to T3788

The CVS loader creates files on the local file system based on
paths which were read from a local copy of a CVS repository or
sent by a CVS server as part of its "cvs rlog" response.

Ensure that such paths will not be able to escape the temporary
directory which stores checked out versions of files.

This also drops spurious copyright headers to those files if present.

Related to T3812

The existing code was probably made out of the svn loader and got never changed. This
drops the inexistant parameters and keep only the one needed.

This also adds coverage to the module.

Related to T3788

Our expansion of the Log keyword was slightly wrong. We need to
trim trailing whitespace from the "prefix" line content which
preceeds the Log keyword when we write out line content which
followed the Log keyword. Update the Log expansion example given
in a comment to document this (see there for details; this behaviour
of CVS is hard to explain without illustration).

Found while testing conversion of the OpenBSD CVS repository.
Add a new test which uses an RCS file from this repository to
reproduce this problem.

CVS supports the definition of custom keywords. A common use case
for custom keywords is to use the project name as a keyword. This
avoids confusion when files are copied between projects using CVS,
in case files contain a keyword that is in use by both projects.
In other words, a file will retain its expanded custom keyword from
project A, allowing to trace the initial file version back to its
origin, after the file was copied into project B's CVS repository.

This feature is in active use by OpenBSD and NetBSD, for example.
Existing conversions of their CVS repositories to Git expand
the corresponding custom keywords as well, and so should we.
Historically, X11 and FreeBSD were also using custom keywords.

During conversion via rsync:// we copy the CVSROOT directory and the
desired CVS module from the rsync server. The file CVSROOT/config
contains directives which configure the use of custom keywords.
Parse this file and expand keywords accordingly when checking out
versions of files from our local copy of the CVS repository.

For now, we only support custom keywords which correspond to the
Id keyword since this is known to be in common use by projects.
The latest releases of CVS (1.12.x) have optional support for arbitrary
keyword aliases via custom keywords. Support for this could be added
later, should there be a need to do so. In any case, the pserver access
method already supports arbitrary custom keywords because such keywords
will be expanded by the CVS server when we check out files from it.

While here, optimize our use of rsync a bit.
Fetch only CVSROOT and the desired CVS module over rsync, rather
than fetching the entire CVS repository directory, which may contain
unrelated CVS modules that require disk space but will not be used.