Some remarks:

* Note that Meson adds a hard dependency on Python 3.

* All dependencies and defines are now listed together.

* Some build files were put in their respective subdirectories, e.g. the Geary
  engine library will be built from the Meson file in `src/engine`.

* `--fatal-warnings` is no longer an explicit flag, as Meson provides
  `-Dwerror=true` for this.

* An explicit resource file needs to be used. The issue to support this from
  Meson itself can be found at https://github.com/mesonbuild/meson/issues/706 .

* The `gnome.yelp()` function parses a LINGUAS file so we no longer need to keep
  track of all languages in our build system.

* There are no Debian scripts defined in the meson.build files to keep them
  clean, but they can be kept as separate scripts in `build-aux`.

* Left out the `dist` target as there is now `ninja dist`

* `geary-docs` is disabled by default, as valadoc-0.38.3 returns errors.

https://bugzilla.gnome.org/show_bug.cgi?id=7...