MustParseReference only accepts consts

[imjasonh]

Fixes #963

[codecov-io]

Codecov Report

Merging #964 (ab83f83) into main (d5f9e2c) will increase coverage by 0.05%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #964      +/-   ##
==========================================
+ Coverage   73.08%   73.13%   +0.05%     
==========================================
  Files         107      107              
  Lines        4796     4828      +32     
==========================================
+ Hits         3505     3531      +26     
- Misses        775      780       +5     
- Partials      516      517       +1     

Impacted Files	Coverage Δ
pkg/name/ref.go	100.00% <100.00%> (ø)
pkg/registry/manifest.go	93.29% <0.00%> (-2.68%)	⬇️
pkg/registry/registry.go	100.00% <0.00%> (ø)

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[jonjohnsonjr]

lgtm

[dekkagaijin]

lgtm, very sneaky sir