feat: env expand contents

[caarlos0]

closes #719

[cloudflare-workers-and-pages]

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[codecov]

Codecov Report

Merging #721 (33f1b30) into main (32c34dd) will increase coverage by 0.10%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #721      +/-   ##
==========================================
+ Coverage   75.08%   75.18%   +0.10%     
==========================================
  Files          10       10              
  Lines        2412     2422      +10     
==========================================
+ Hits         1811     1821      +10     
  Misses        425      425              
  Partials      176      176              

Files	Coverage Δ
files/files.go	76.64% <ø> (ø)
nfpm.go	85.65% <100.00%> (+0.59%)	⬆️

[djgilcrease]

Careful with this as we have rejected this in the past because $ is a valid path character. So we need tests for that and need to document that if a $ is in the path it needs to be escaped.

[AlekSi]

[AlekSi]

Another option is to opt-in into expanding:

contents:
- src: '${NAME}_${ARCH}'
  dst: /usr/bin/${NAME}
  expand: true

[djgilcrease]

Another option is to opt-in into expanding:

I like this solution, that way it is explicit that the user knows it will expand env vars

[caarlos0]

pushed

[djgilcrease]

LGTM