Add docs generation command

[pavolloffay]

Resolves #1537

docs PR: jaegertracing/documentation#257

Signed-off-by: Pavol Loffay ploffay@redhat.com

[codecov]

Codecov Report

Merging #1572 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master   #1572      +/-   ##
=========================================
+ Coverage   98.79%   98.8%   +<.01%     
=========================================
  Files         190     191       +1     
  Lines        9063    9102      +39     
=========================================
+ Hits         8954    8993      +39     
  Misses         85      85              
  Partials       24      24

Impacted Files	Coverage Δ
cmd/docs/command.go	100% <100%> (ø)

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[yurishkuro]

lgtm

actually, I don't think pre-formatted output in .md file is the best format. I see that blackfriday supports HTML output, not sure if it makes a different and/or of cobra can generate HTML.

[pavolloffay]

Cobra can also output html and man pages. We could even make it configurable via a flag.

Most importantly we should go with a format which can be embedded to our docs. I am not sure if we can easily embed there htlm. The markdown can be easily embedded see the PR to the website.

[pavolloffay]

actually, I don't think pre-formatted output in .md file is the best format. I see that blackfriday supports HTML output, not sure if it makes a different and/or of cobra can generate HTML.

actually cobra cannot generate html, I have added a flag to generate output in md, rst and man format.

[pavolloffay]

@yurishkuro one last thing. Do we like more jaeger docs or jaeger gen docs. The later is more flexible if we add more gen commands (e.g. auto-completion).