GitHub flakes don't provide revCount.

Flakes now are evaluated in pure mode, so we can't rely on
currentSystem anymore.

opencv2 is essentially EOL and has security concerns

NixOS has `virtualisation.docker.autoPrune.enable` for this
functionality; we should not do it every time a container starts up.

(also, some trivial documentation fixes)

* bash-my-aws: init at 20191231

Create bma-init

* Update

The old variant is still working but setting "cafile" is deprecated
since version 3.6 [0] and generates a warning:
DeprecationWarning: cafile, capath and cadefault are deprecated, use a custom context instead.

But without this patch "fetchRepoProject" still fails with
"error no host given" (see 337380ea1d).

[0]: https://docs.python.org/3.7/library/urllib.request.html#urllib.request.urlopen

pythonPackages.hglib: fix tests

In 87a19e9048 I merged staging-next into master using the GitHub gui as intended.
In ac241fb7a5 I merged master into staging-next for the next staging cycle, however, I accidentally pushed it to master.
Thinking this may cause trouble, I reverted it in 0be87c7979. This was however wrong, as it "removed" master.

This reverts commit 0be87c7979.

google-cloud-sdk: reduce output size

I merged master into staging-next but accidentally pushed it to master.
This should get us back to 87a19e9048.

This reverts commit ac241fb7a570d6cf81d229ad22a8889602639160, reversing
changes made to 76a439239e.

Staging next

https://github.com/hashicorp/vagrant/releases/tag/v2.2.7

electron*: refactor 4+ to common expression, add 7 and 8, updates

The service needed lots of changes. A few smaller changes
are added into the PR, e.g. replacement for PR #72014.
See the commit messages for details.

https://gitlab.labs.nic.cz/knot/knot-resolver/tags/v5.0.1

https://lists.zx2c4.com/pipermail/wireguard/2020-February/004962.html

https://github.com/documize/community/releases/tag/v3.7.0

* print-hashes.nix uses upstream-provided SHA256SUMS file
* electron_4: 4.2.8 -> 4.2.12
* electron_5: 5.0.8 -> 5.0.13
* electron_6: 6.0.1 -> 6.1.7
* electron_7:: init at 7.1.10

FWIW:
electron_4 previously did not include at-spi2-core, only at-spi2-atk.
Both are now included, matching other versions for a slightly simpler
expression.

SPAdes: 3.13.1 -> 3.14.0

sudo: 1.8.30 -> 1.8.31

use overlayfs by default for netboot and iso

paraview: add wrapQtAppsHook

sequoia: 0.11.0 -> 0.13.0

And better document why id3 is there

In addition, review function signature formatting.

bazelisk: 1.2.1 -> 1.3.0

unrar: 5.8.5 -> 5.9.1