docs: new maintainer notes

docs/contributing.rst

@@ -46,17 +46,6 @@ Style guide: Is it OCRmyPDF or ocrmypdf?
 
 The program/project is OCRmyPDF and the name of the executable or library is ocrmypdf.
 
-Known ports/packagers
-=====================
-
-OCRmyPDF has been ported to many platforms already. If you are interesting in
-porting to a new platform, check with
-`Repology <https://repology.org/projects/?search=ocrmypdf>`__ to see the status
-of that platform.
-
-Packager maintainers, please ensure that the command line completion scripts in
-``misc/`` are installed.
-
 Copyright and license
 =====================
 

docs/index.rst

@@ -40,6 +40,7 @@ image processing and OCR to existing PDFs.
    plugins
    apiref
    contributing
+   maintainers
 
 Indices and tables
 ==================

docs/maintainers.rst

@@ -0,0 +1,60 @@
+================
+Maintainer notes
+================
+
+This is for those who package OCRmyPDF for downstream use.  (Thank you 
+for your hard work.)
+
+Known ports/packagers
+=====================
+
+OCRmyPDF has been ported to many platforms already. If you are interesting in
+porting to a new platform, check with
+`Repology <https://repology.org/projects/?search=ocrmypdf>`__ to see the status
+of that platform.
+
+Make sure you can package pikepdf
+---------------------------------
+
+pikepdf, created by the same author, is a mixed Python and C++14 package with
+much stiffer build requirements. If you want to use OCRmyPDF on some novel platform
+or distribution, first make sure you can pikepdf.
+
+Non-Python dependencies
+-----------------------
+
+Note that we have non-Python dependencies. In particular, OCRmyPDF requires
+Ghostscript and Tesseract OCR to be installed and needs to be able to locate their
+binaries on the system PATH. On Windows, OCRmyPDF will also check the registry 
+for their locations.
+
+Tesseract OCR relies on SIMD for performance and only has proper support for this
+on ARM and x86_64. Performance may be poor on other processor architectures.
+
+Versioning scheme
+-----------------
+
+OCRmyPDF uses setuptools-scm for versioning, which requires derives the version from
+Git as a single source of truth. This may be unsuitable for some distributions, e.g.
+to indicate that your distribution modifies OCRmyPDF in some way.
+
+You can patch the ``__version__`` variable in ``src/ocrmypdf/_version.py`` if 
+necessary.
+
+OCRmyPDF uses setuptools-scm-git-archive to ensure that tarballs downloaded from
+GitHub contain version information. Unfortunately, these tarballs are not always
+deterministic. See this 
+`issue <https://github.com/jbarlow83/OCRmyPDF/issues/841#issuecomment-936562696>`_.
+
+jbig2enc
+--------
+
+OCRmyPDF will use jbig2enc, a JBIG2 encoder, if one can be found. Some distributions
+have shied away from packaging JBIG2 because it contains patented algorithms, but
+all patents have expired since 2017. If possible, consider packaging it too to
+improve OCRmyPDF's compression.
+
+Command line completions
+------------------------
+
+Please ensure that command line completions are installed.