Opentimestamps timestamper

[meeDamian]

After #10 is done, create an image that allows to timestamp git tags without effectively locking the ability to create commits on said machine in the meantime.

Do it by:

1. volume to source directory

2. volume to host git configuration

3. volume to host gpg key

4. .gitconfig contains:

   …
   [gpg]
   	program = /path/to/opentimestamps-client/ots-git-gpg-wrapper.sh

5. ots-git-gpg-wrapper.sh is modified to contain --wait flag

6. entrypoint does git tag

7. Creating an upgraded git-tag should look like:

   docker run --rm -it \
   	-v "$(pwd):/src/" \
   	-v "${HOME}/.gitconfig:/data/.gitconfig:ro" \
   	-v "some paths for GPG:ro" \
   	lncm/ots-tag -sa 'TAG' -m 'DESC'