Use ar & tar instead of dpkg -x

[jwodder]

Closes #85.

[codecov-commenter]

Codecov Report

Merging #86 (570fd0a) into master (826a617) will decrease coverage by 0.32%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master      #86      +/-   ##
==========================================
- Coverage   63.09%   62.76%   -0.33%     
==========================================
  Files           1        1              
  Lines        1157     1163       +6     
  Branches      217      218       +1     
==========================================
  Hits          730      730              
- Misses        363      369       +6     
  Partials       64       64              

Impacted Files	Coverage Δ
src/datalad_installer.py	62.76% <0.00%> (-0.33%)	⬇️

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[yarikoptic]

note: although unlikely to matter here chdir within a process is a bit "atrocious" , e.g. IIRC getcwd would return a resolved directory name if you are in a dir which is symlinked somewhere. I thought to suggest to use --output option for ar I find available on Debian 2.35.2, but it seems to be not available on centos with 2.27-27.base.el7. So let's keep chdiring I guess

[yarikoptic]

Looks LGTM, thank you!
just to make sure (since we have no test coverage for this) - did you try it out on some linux box?

[jwodder]

@yarikoptic Yes, I tested it in a Docker container.

[yarikoptic]

Great, thank you! Let's proceed