Related: obfs4#33736

Some lines has changed, let's use the latest format until
tpo/core/tor#29128 is fixed.

Closes: #4

In addition to basic variables OR_PORT, PT_PORT and EMAIL, it is now
possible to enable additional variables support for extra configuration
tweaks. Having OBFS4_ENABLE_ADDITIONAL_VARIABLES set to 1, all the
variables prefixed with OBFS4V_ (with their values) are passed to torrc
(with prefix removed). That make it possible to configure virtually
everything using environment variables.

For example:
OBFS4_ENABLE_ADDITIONAL_VARIABLES=1
OBFS4V_AccountingStart=day 0:00
OBFS4V_AccountingMax=10 GBytes
OBFS4V_RelayBandwidthRate=200 KBytes
OBFS4V_RelayBandwidthBurst=1000 KBytes

will generate:
AccountingStart day 0:00
AccountingMax 10 GBytes
RelayBandwidthRate 200 KBytes
RelayBandwidthBurst 1000 KBytes

in /etc/tor/torrc. The variables or put after the basic variables and or
displayed (with the corresponding values) during the container start.

We now own the organisation <https://hub.docker.com/orgs/thetorproject>,
so there's no need to continue using my user account.

Fixed the file name of tor's apt repository

* Extend documentation.

* "Downgrade" to version 3.4 of the file format -- the minimum required
  version.

* Remove the IMAGE and VERSION environment variables.

After tor is restarted, its log can contain duplicates, which would mess
up the output of get-bridge-line.  This commit adds a 'tail -1' to
filter out these duplicates.  Thanks to thymbahutymba for pointing out
this issue.

This fixes <https://bugs.torproject.org/31834>.

fix how the ip is got if it is changed

After tor is restarted, its log can contain duplicates, which would mess
up the output of get-bridge-line.  This commit adds a 'tail -1' to
filter out these duplicates.  Thanks to thymbahutymba for pointing out
this issue.

This fixes <https://bugs.torproject.org/31834>.

This results in an image size decrease from ~120 MB to ~70 MB.

This patch also adds libcap2-bin to our list of installed packages
because the debian-slim image doesn't ship it.

This fixes <https://bugs.torproject.org/32860>.  Thanks to qdii for
filing this ticket and proposing a fix!

This makes it possible to run multiple containers on one machine by
running 'make deploy' once for each deployment:

  make deploy OR_PORT=1234 PT_PORT=4321 EMAIL=foo
  make deploy OR_PORT=2345 PT_PORT=5432 EMAIL=foo
  ...

This commit replaces the 'test -n' invocations with a more complex
construct, which is only shown if the required arguments are missing.
Running 'make deploy' will now result in:

  Env var OR_PORT is not set.
  make: *** [Makefile:21: deploy] Error 1

The script deploy-container.sh automatically determines open ports for
the operator.  That's not optimal because we should encourage operators
to think about and pick their own ports.  This commit replaces
deploy-container.sh with a Makefile.  Operators can now deploy an obfs4
bridge by running:

  OR_PORT=1111 PT_PORT=2222 EMAIL=foo@bar.com make deploy

The new Makefile also uses docker's --volume parameter to make Tor's
data directory permanent.

Thanks to thymbahutymba for coming up with a Makefile that inspired this
commit: <https://bugs.torproject.org/31834#comment:5>

This allows docker to show tor's logs when running:

  docker logs CONTAINER_ID

Debian's repository provides tor's LTS version, which doesn't
necessarily give us the latest stable version.