Add --no-deps flag to pip-sync, which is simply passed through to pip install

[AndydeCleyre]

--no-deps can now be provided to pip-sync, whereby --no-deps will be passed through to pip install, and un-locked deps of locked requirements will be either removed or not installed in the first place, in order to match the lockfile exactly, despite breaking package dependencies.

Changelog-friendly one-liner: pip-sync now accepts --no-deps, to match locked txts exactly, ignoring any unlocked dependencies

Contributor checklist

• Provided the tests for the changes.
• 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 #987 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #987      +/-   ##
==========================================
+ Coverage   99.11%   99.11%   +<.01%     
==========================================
  Files          34       34              
  Lines        2360     2363       +3     
  Branches      302      303       +1     
==========================================
+ Hits         2339     2342       +3     
  Misses         11       11              
  Partials       10       10

Impacted Files	Coverage Δ
tests/test_cli_sync.py	100% <ø> (ø)	⬆️
piptools/scripts/sync.py	100% <100%> (ø)	⬆️

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[atugushev]

LGTM 👍 Thanks, @AndydeCleyre!

[atugushev]

@AndydeCleyre

Just wondering, why do you prefer to mark tasks this way:

[✓] Provided the tests for the changes.

instead of

[x] Provided the tests for the changes.

wich is the current Github's markdown syntax? See the doc.

With the first one we get this progress bar on PRs list (note the progress-bar):

The second one marks tasks correctly (note the progress-bar):

[AndydeCleyre]

Just wondering, why do you prefer to mark tasks this way?

Just because I never read those docs, and generally think of a check as "yes" and an x as "no," but thank you, now I know better.

[atugushev]

@AndydeCleyre

There is an issue #321 the implementation of which can supersede this PR. Let me know what you think of it.

[AndydeCleyre]

@atugushev If --no-deps functionality is enabled by an implementation for #321 that's great and should be merged instead. My only interest here is that there be an acceptable interface for people who don't want #907 behavior, so we can fix #896 and its sub-issue of sync behavior inconsistency.

Inviting @ulope and @Zac-HD to comment

[atugushev]

Close this in favor of #1080.