feat(Algebra/Homology): homotopy equivalences in degreewise split short exact sequences

[joelriou]

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[github-actions]

PR summary bbd59509be

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference
Mathlib.Algebra.Homology.Embedding.Splitting (new file)	1026
Mathlib.Algebra.Homology.HomotopyCategory.ChainComplex (new file)	1338

---

Declarations diff (regex)

+ extendFunctorCompEvalIso
+ homotopyEquivalences_shortComplexF_iff_of_degreewiseSplit
+ homotopyEquivalences_shortComplexF_iff_of_splitting
+ homotopyEquivalences_shortComplexG_iff_of_degreewiseSplit
+ homotopyEquivalences_shortComplexG_iff_of_splitting
+ ofIsZero
+ splittingExtend
+ splittingExtend_apply
+ trianglehOfDegreewiseSplit_distinguished

You can run this locally as follows

## from your `mathlib4` directory:
git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci

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

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

The doc-module for scripts/pr_summary/declarations_diff.sh in the mathlib-ci repository contains some details about this script.

Declarations diff (Lean)

✅ Lean-aware diff — post-build, computed from the Lean environment (commit bbd5950).

• +9 new declarations
• −0 removed declarations

+CategoryTheory.ShortComplex.Splitting.ofIsZero
+ChainComplex.homotopyEquivalences_shortComplexF_iff_of_degreewiseSplit
+ChainComplex.homotopyEquivalences_shortComplexG_iff_of_degreewiseSplit
+CochainComplex.homotopyEquivalences_shortComplexF_iff_of_splitting
+CochainComplex.homotopyEquivalences_shortComplexG_iff_of_splitting
+CochainComplex.trianglehOfDegreewiseSplit_distinguished
+ComplexShape.Embedding.extendFunctorCompEvalIso
+ComplexShape.Embedding.splittingExtend
+ComplexShape.Embedding.splittingExtend_apply

---

Increase in strong tech debt: (relative, absolute) = (1.38, 0.00)

Current number	Change	Type (strong)
4367	1	backward.defeqAttrib.useBackward
6994	2	backward.isDefEq.respectTransparency

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

Current number	Change	Type (weak)
5049	2	exposed public sections

Current commit bbd59509be
Reference commit 1f8806b67d

This script lives in the mathlib-ci repository. To run it locally, from your mathlib4 directory:

git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci
../mathlib-ci/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).