[Merged by Bors] - feat(CategoryTheory/Sites): Over.post F preserves covers if F does

[chrisflav]

We also show the lifting covers variant. Notably, we don't show that Over.post F is continuous if F is. This would follow for example from showing that sheaves on Over X are sheaves on C over yoneda.obj X, which we don't have yet.

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[github-actions]

PR summary 16cc871c27

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

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Declarations diff

+ _root_.CategoryTheory.CoverPreserving.overPost
+ instance {D : Type*} [Category* D] (K : GrothendieckTopology D)
+ overEquiv_functorPullback_post
+ overEquiv_functorPushforward_post
++ post_forget_eq_forget_comp

You can run this locally as follows

## summary with just the declaration names:
./scripts/pr_summary/declarations_diff.sh <optional_commit>

## more verbose report:
./scripts/pr_summary/declarations_diff.sh long <optional_commit>

The doc-module for scripts/pr_summary/declarations_diff.sh contains some details about this script.

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Increase in tech debt: (relative, absolute) = (2.00, 0.00)

Current number	Change	Type
6458	2	backward.isDefEq.respectTransparency

Current commit 07e5fa17ad
Reference commit 16cc871c27

You can run this locally as

./scripts/reporting/technical-debt-metrics.sh pr_summary

• The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
• The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).

[joelriou]

Thanks!

bors d+

[mathlib-bors]

✌️ chrisflav can now approve this pull request. To approve and merge a pull request, simply reply with bors r+. More detailed instructions are available here.

[chrisflav]

Thanks for the review!
bors r+

[mathlib-bors]

Pull request successfully merged into master.

Build succeeded:

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• ci (staging) / Post-Build Step