Convert CONTRIBUTING.rst to CONTRIBUTING.md.

CONTRIBUTING.md

+# Contributing
+
+The preferred way to report bugs about *diffoscope*, as well as suggest
+fixes and requests for improvements, is to submit reports to the issue
+tracker at:
+
+    https://salsa.debian.org/reproducible-builds/diffoscope/issues
+
+You can also submit patches via *Merge Request* on Salsa, Debian's
+Gitlab instance. Start by forking the
+[`diffoscope` Git repository](https://salsa.debian.org/reproducible-builds/diffoscope)
+(see [documentation](https://salsa.debian.org/help/gitlab-basics/fork-project.md)),
+make your changes and commit them as you normally would. You can then push your
+changes and submit a *merge request* via Salsa. See:
+[Gitlab documentation](https://salsa.debian.org/help/gitlab-basics/add-merge-request.md)
+about *Merge Requests*.
+
+You can also submit bugs about Debian specific issues to the Debian bug
+tracker.
+
+## Testing
+
+diffoscope's test suite relies on [pytest](https://docs.pytest.org/);
+to run all tests use `pytest[-3]`, appending `-n 4` or similar to enable
+running tests concurrently. For faster interactive development here's
+an example of how to run a (much) smaller subset of tests:
+
+    $ pytest -v --exitfirst -k lib tests/comparators/test_elf.pyc [-pdb]
+
+More options are available at `[pytest -h]`.
+
+## Add a comparator
+
+Diffoscope doesn't support a specific file type? Please contribute to
+the project! Each file type is handled by a comparator, and writing a
+new one is usually very easy. Here are the steps to add a new
+comparator:
+
+-   Add the new comparator in `diffoscope/comparators/` (have a look at
+    the other comparators in the same directory to have an idea of what
+    to do)
+-   Declare the comparator File class in `ComparatorManager` in
+    `diffoscope/comparators/__init__.py`
+-   Add a test in `tests/comparators/`
+-   If required, update the `Build-Depends` list in `debian/control`
+-   If required, update the `EXTERNAL_TOOLS` list in
+    `diffoscope/external_tools.py`
+
+## Uploading the package
+
+When uploading diffoscope to the Debian archive, please take extra care
+to make sure the uploaded source package is correct, that is it includes
+the files tests/data/test(1o) which in some cases are removed by
+dpkg-dev when building the package.
+
+See [#834315](https://bugs.debian.org/834315) for an example FTBFS bug
+caused by this. (See [#735377](https://bugs.debian.org/735377#44)
+and followups to learn how this happened and how to prevent it)
+
+Please also release a signed tarball:
+
+    $ VERSION=FIXME
+    $ git archive --format=tar --prefix=diffoscope-${VERSION}/ ${VERSION} | bzip2 -9 > diffoscope-${VERSION}.tar.bz2
+    $ gpg --detach-sig --armor --output=diffoscope-${VERSION}.tar.bz2.asc < diffoscope-${VERSION}.tar.bz2
+
+And commit them to our LFS repository at:
+
+    https://salsa.debian.org/reproducible-builds/reproducible-lfs
+
+After uploading, please also update the version on PyPI using:
+
+    $ python3 setup.py sdist upload --sign
+
+Once the tracker.debian.org entry appears, consider tweeting the release
+on `#reproducible-builds` with:
+
+    %twitter diffoscope $VERSION has been released. Check out the changelog here: $URL
+
+Finally, update the Docker image using:
+
+    $ docker build -t registry.salsa.debian.org/reproducible-builds/diffoscope .
+    $ docker push registry.salsa.debian.org/reproducible-builds/diffoscope

CONTRIBUTING.rst

-Contributing
-============
-
-The preferred way to report bugs about diffoscope, as well as suggest fixes and
-requests for improvements, is to submit reports to the issue tracker at
-https://salsa.debian.org/reproducible-builds/diffoscope/issues
-
-You can also submit patches via *merge request* to Salsa, Debian's Gitlab. Start
-by forking the `diffoscope Git
-repository <https://salsa.debian.org/reproducible-builds/diffoscope>`__
-(see
-`documentation <https://salsa.debian.org/help/gitlab-basics/fork-project.md>`__),
-make your changes and commit them as you normally would. You can then push your
-changes and submit a *merge request* via Salsa.  See `Gitlab documentation
-<https://salsa.debian.org/help/gitlab-basics/add-merge-request.md>`__ about
-*merge requests*.
-
-You can also submit bugs about Debian specific issues to the Debian bug tracker. 
-
-Testing
-=======
-
-diffoscope's test suite relies on `pytest <https://docs.pytest.org/>`__;
-to run all tests use ``pytest[-3]``, appending ``-n 4`` or similar to enable
-running tests concurrently. For faster interactive development here's an
-example of how to run a (much) smaller subset of tests:
-
-    pytest  -v --exitfirst -k lib tests/comparators/test_elf.pyc [ --pdb ]
-
-More options in `pytest -h`.
-
-Add a comparator
-================
-
-Diffoscope doesn't support a specific file type? Please contribute to the
-project! Each file type is handled by a comparator, and writing a new one is
-usually very easy.
-Here are the steps to add a new comparator:
-
-- Add the new comparator in ``diffoscope/comparators/`` (have a look at the
-  other comparators in the same directory to have an idea of what to do)
-- Declare the comparator File class in ``ComparatorManager`` in
-  ``diffoscope/comparators/__init__.py``
-- Add a test in ``tests/comparators/``
-- If required, update the ``Build-Depends`` list in ``debian/control``
-- If required, update the ``EXTERNAL_TOOLS`` list in
-  ``diffoscope/external_tools.py``
-
-Uploading the package
-=====================
-
-When uploading diffoscope to the Debian archive, please take extra care to make
-sure the uploaded source package is correct, that is it includes the files
-tests/data/test(1|2).(a|o) which in some cases are removed by dpkg-dev when
-building the package. See `#834315 <https://bugs.debian.org/834315>`__ for an example
-FTBFS bug caused by this. (See `#735377
-<https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=735377#44>`__ and followups
-to learn how this happened and how to prevent it)
-
-Please also release a signed tarball::
-
-    $ VERSION=FIXME
-    $ git archive --format=tar --prefix=diffoscope-${VERSION}/ ${VERSION} | bzip2 -9 > diffoscope-${VERSION}.tar.bz2
-    $ gpg --detach-sig --armor --output=diffoscope-${VERSION}.tar.bz2.asc < diffoscope-${VERSION}.tar.bz2
-
-And commit them to our LFS repository at https://salsa.debian.org/reproducible-builds/reproducible-lfs
-
-After uploading, please also update the version on PyPI using::
-
-   $ python3 setup.py sdist upload --sign
-
-Once the tracker.debian.org entry appears, consider tweeting the release on
-``#reproducible-builds`` with::
-
-  %twitter diffoscope $VERSION has been released. Check out the changelog here: $URL
-
-Finally, update the Docker image using::
-
-    docker build -t registry.salsa.debian.org/reproducible-builds/diffoscope .
-    docker push registry.salsa.debian.org/reproducible-builds/diffoscope