Tsrc

Fix some incorrect URLs in the project's metadata and some other places.

Breaking: correct branch on sync

If any of the repositories is not on the configured branch, but it is
clean then the branch is changed to the configured one and then the
repository is updated. Otherwise that repository will not be not updated.

Previously, `tsrc sync` would print an error and *not* checkout the branch.

To have `tsrc sync` behave like this, use the new `--no-correct-branch` flag.

Breaking: add --singular-remote argument to tsrc sync too

In `tsrc 2.7` you could use `-r` in `tsrc init` to only use one
remote. But you had no way to pass the same option to `tsrc sync`.

In this version, you can use `-r` or `--singular-remote` for both
`tsrc init` and `tsrc sync`

Unfortunately , this means you must now use `-i, --include <regex>`
instead of of `-r <regex>` when selecting repositories based on a regex.

Implemented by:

* Albert De La Fuente Vigliotti
* Greg Dubicki
* Dimitri Merejkowsky

Original issue reportedy by Maxime Réty

Other changes

* When running git commands, don't capture standard error along side standard out - fixes
381, reported by Patrick Decat.
* Bump minimum supported version to Python **3.8**.
* Add support for Python 3.12.
* Bump `ruamel.yaml`, `dparse`.
* Don't hide cloning errors when running in parallel.
* Doc improvements (patches by Henry Chang).

In addition to preserving the order repos are listed in the manifest,
`tsrc` now makes sure repos included via groups are processed before
the other repos. See 356 for details. Thanks to raabf for the bug report
and code review !

* Show which git commands are run by default.
* `tsrc init`: fix order of operations - clone the local manifest *before*
writing the workspace configuration. Fixes 344, where users could not run `init` a second
time if the previous call failed. Bug report by cgestes.
* `tsrc init`: do not assume the default branch of the manifest is `master`. Note that `master` is still hard-coded in a few places. See 347 for details.
* When using `-j 1`, do not sort repositories by lexical order of destination, but preserve
the order in which they were specified in the manifest. Suggested by raabf.

* Allow to use `python -m tsrc` in addition to just `tsrc`
* Documentation updates
* Bump `mypy`

Highlights

* Bump minimum supported version to Python **3.7**.
* Introduce `ignore_submodules` repository option - Patch by Thomas Hiscock.
* When `-j` is not used, try getting the default `jobs` value from the
`TSRC_PARALLEL_JOBS` environment variable. Patch by Marcin Jaworski.

Other

* Bump mkdocs from 1.2.2 to 1.2.3
* Bump pygit2
* Bump linters (flake8, mypy, black)
* Remove dependency on `attr`