This is analogous to the 3.7-related CI change in gitdb that waspart ofgitpython-developers/gitdb#114, asto part ofgitpython-developers/smmap#58.Since some tests are not yet passing on 3.13, this does not add3.13 to CI, nor to the documentation of supported versions in`setup.py`. Note that the list there is not enforced; GitPython canalready be installed on Python 3.13 and probably *mostly* works.(Seegitpython-developers#1955for details on other changes that should be made to fully supportrunning GitPython on Python 3.13.)

Sincegitpython-developers#1987, test jobs from `pythonpackage.yml` appear in anunintuitive order, and some show an extra bool matrix variable intheir names while others don't (this corresponds to `experimental`,which was always set to some value, but was set in different ways).This fixes that by:- Listing all tested versions, rather than introducing some in an  `include` key. (The `include:`-introduced jobs didn't distinguish  between originally-present matrix variables and those that are  introduced based on the values of the original ones.)- Replacing `os` with `os-type`, which has only the first part of  the value for `runs-on:` (e.g., `ubuntu`), and adding `os-ver`  to each matrix job, defaulting it to `latest`, but using `22.04`  for Python 3.7 on Ubuntu.This should also naturally extend to adding 3.13, with or withoutsetting `continue-on-error` to temporarily work around the problemsobseved ingitpython-developers#1955, but nothing 3.13-related is done in this commit.

As this is being integrated, Python 3.13 is no longer a releasecandidate, but this marks it experimental since that might also beused temporarily to prevent some of the failures mentioned ingitpython-developers#1955from failing the workflow.But right now this allows the workflow to fail.

Sincegitpython-developers#1987, test jobs from `pythonpackage.yml` appear in anunintuitive order, and some show an extra bool matrix variable intheir names while others don't (this corresponds to `experimental`,which was always set to some value, but was set in different ways).This fixes that by:- Listing all tested versions, rather than introducing some in an  `include` key. (The `include:`-introduced jobs didn't distinguish  between originally-present matrix variables and those that are  introduced based on the values of the original ones.)- Replacing `os` with `os-type`, which has only the first part of  the value for `runs-on:` (e.g., `ubuntu`), and adding `os-ver`  to each matrix job, defaulting it to `latest`, but using `22.04`  for Python 3.7 on Ubuntu.This should also naturally extend to adding 3.13, with or withoutsetting `continue-on-error` to temporarily work around the problemsobseved ingitpython-developers#1955, but nothing 3.13-related is done in this commit.

As this is being integrated, Python 3.13 is no longer a releasecandidate, but this marks it experimental since that might also beused temporarily to prevent some of the failures mentioned ingitpython-developers#1955from failing the workflow.But right now this allows the workflow to fail.

It is specifically that combination that breaks some things. Theunderlying cause is a change in `isabs` to correctly report thatpaths on Windows that start with `\` that is not part of aconstruction such as `\\?\` are not absolute paths. (Seegitpython-developers#1955 andlinks therein.) The change to `isabs` starts in 3.13, and it isonly applicable to Windows, so only that combination is affected.

Sincegitpython-developers#1987, test jobs from `pythonpackage.yml` appear in anunintuitive order, and some show an extra bool matrix variable intheir names while others don't (this corresponds to `experimental`,which was always set to some value, but was set in different ways).This fixes that by:- Listing all tested versions, rather than introducing some in an  `include` key. (The `include:`-introduced jobs didn't distinguish  between originally-present matrix variables and those that are  introduced based on the values of the original ones.)- Replacing `os` with `os-type`, which has only the first part of  the value for `runs-on:` (e.g., `ubuntu`), and adding `os-ver`  to each matrix job, defaulting it to `latest`, but using `22.04`  for Python 3.7 on Ubuntu.This should also naturally extend to adding 3.13, with or withoutsetting `continue-on-error` to temporarily work around the problemsobseved ingitpython-developers#1955, but nothing 3.13-related is done in this commit.

As this is being integrated, Python 3.13 is no longer a releasecandidate, but this marks it experimental since that might also beused temporarily to prevent some of the failures mentioned ingitpython-developers#1955from failing the workflow.But right now this allows the workflow to fail.

It is specifically that combination that breaks some things. Theunderlying cause is a change in `isabs` to correctly report thatpaths on Windows that start with `\` that is not part of aconstruction such as `\\?\` are not absolute paths. (Seegitpython-developers#1955 andlinks therein.) The change to `isabs` starts in 3.13, and it isonly applicable to Windows, so only that combination is affected.

But not Windows yet (gitpython-developers#1955).

As this is being integrated, Python 3.13 is no longer a releasecandidate, but this marks it experimental since that might also beused temporarily to prevent some of the failures mentioned ingitpython-developers#1955from failing the workflow.But right now this allows the workflow to fail.

It is specifically that combination that breaks some things. Theunderlying cause is a change in `isabs` to correctly report thatpaths on Windows that start with `\` that is not part of aconstruction such as `\\?\` are not absolute paths. (Seegitpython-developers#1955 andlinks therein.) The change to `isabs` starts in 3.13, and it isonly applicable to Windows, so only that combination is affected.

For now, this omits macOS and Windows from the 3.13t ("threaded")tests.The plan ingitpython-developers#2005 is to start without them, and no OS-specificproblems have been identified so far. In particular, in theprevious commit that adds 3.13t without excluding any operatingsystems, all tests in the macOS job passed as expected, and theWindows job had the same failure with the same message as ingitpython-developers#1955,with no XFAIL changed to XPASS (which, if present, would suggestGC differences meriting further exploration of 3.13t on Windows).

For now, this omits macOS and Windows from the 3.13t ("threaded")tests.The plan ingitpython-developers#2005 is to start without them, and no OS-specificproblems have been identified so far. In particular, in theprevious commit that adds 3.13t without excluding any operatingsystems, all tests in the macOS job passed as expected, and theWindows job had the same failure with the same message as ingitpython-developers#1955,with no XFAIL changed to XPASS (which, if present, would suggestGC differences meriting further exploration of 3.13t on Windows).

For now, this omits macOS and Windows from the 3.13t ("threaded")tests.The plan ingitpython-developers#2005 is to start without them, and no OS-specificproblems have been identified so far. In particular, in theprevious commit that adds 3.13t without excluding any operatingsystems, all tests in the macOS job passed as expected, and theWindows job had the same failure with the same message as ingitpython-developers#1955,with no XFAIL changed to XPASS (which, if present, would suggestGC differences meriting further exploration of 3.13t on Windows).