Add support for --find-links in pip-compile output

[atugushev]

This adds support to pip-compile for the -f, --find-links flag in the input requirements.in. Rebased #704 and adjusted tests. Thanks @estan for the contribution!

Changelog-friendly one-liner: Add support for --find-links in pip-compile output.

Contributor checklist

• Provided the tests for the changes.
• Requested a review from another contributor.
• Gave a clear one-line description in the PR (that the maintainers can add to CHANGELOG.md on release).
• Assign the PR to an existing or new milestone for the target version (following Semantic Versioning).

[codecov]

Codecov Report

Merging #793 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #793      +/-   ##
==========================================
+ Coverage   98.06%   98.07%   +<.01%     
==========================================
  Files          34       34              
  Lines        1962     1972      +10     
  Branches      256      257       +1     
==========================================
+ Hits         1924     1934      +10     
  Misses         26       26              
  Partials       12       12

Impacted Files	Coverage Δ
tests/test_writer.py	100% <100%> (ø)	⬆️
tests/test_cli_compile.py	100% <100%> (ø)	⬆️
piptools/scripts/compile.py	100% <100%> (ø)	⬆️
piptools/writer.py	100% <100%> (ø)	⬆️

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[suutari]

FYI, I've implemented something similar in #453 over a year ago. Though with the difference that only relative directories are written out, since absolute ones rarely make sense to be stored into the txt file. If this gets merged, then #453 can be closed (or the other way around).

[atugushev]

Hello @suutari,

Thank you for pointing that out! I agree there should be relative links. I'll port your code here if you don't mind.

[atugushev]

@suutari

Though with the difference that only relative directories are written out

I've found an interesting FIXME comment in pip source code:

# FIXME: it would be nice to keep track of the source
# of the find_links: support a find-links local path
# relative to a requirements file.

Maybe it's better to fix this case on the pip side instead of hard coding it in the pip-tools?

[estan]

@atugushev I've been completely swamped and almost forgot about my PR. Thanks for taking care of this!