Always include tag in tarball refs

[jonjohnsonjr]

Fixes #890

[codecov-io]

Codecov Report

Merging #893 (01f33ca) into master (6544cb0) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #893      +/-   ##
==========================================
+ Coverage   72.52%   72.53%   +0.01%     
==========================================
  Files         108      108              
  Lines        4670     4672       +2     
==========================================
+ Hits         3387     3389       +2     
  Misses        773      773              
  Partials      510      510              

Impacted Files	Coverage Δ
pkg/v1/tarball/write.go	61.87% <100.00%> (+0.42%)	⬆️

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