[Merged by Bors] - feat(CategoryTheory/Sites): functors that are 1-hypercover dense

[joelriou]

Let F : C₀ ⥤ C be a functor equipped with Grothendieck topologies J₀ and J. Assume that F is a dense subsite. We introduce a typeclass IsOneHypercoverDense.{w} F J₀ J which roughly says that objects in C admits a 1-hypercover consisting of objects in C₀.

---

[github-actions]

PR summary 71cd708d5e

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference
Mathlib.CategoryTheory.Sites.DenseSubsite.OneHypercoverDense (new file)	995

---

Declarations diff

+ IsOneHypercoverDense
+ I₁'
+ OneHypercoverDenseData
+ PreOneHypercoverDenseData
+ isDenseSubsite_of_isOneHypercoverDense
+ multicospanIndex
+ multicospanMap
+ multicospanMapIso
+ multicospanShape
+ oneHypercoverDenseData
+ sieve₁₀
+ toPreOneHypercover

You can run this locally as follows

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

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

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

---

No changes to technical debt.

You can run this locally as

./scripts/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).

[chrisflav]

Thanks!
maintainer merge

[github-actions]

🚀 Pull request has been placed on the maintainer queue by chrisflav.

[jcommelin]

Thanks 🎉

bors merge

[mathlib-bors]

Pull request successfully merged into master.

Build succeeded:

• ci (staging) / Post-Build Step
• ci (staging) / Build
• ci (staging) / Lint style
• ci (staging) / Post-CI job