feat(Algebra/Homology): the bijection of Ext-groups that is induced by an adjunction between exact functors

[joelriou]

---

• depends on: feat(Algebra/Homology): pseudofunctorial behaviour of Functor.mapDerivedCategory #43089
• depends on: chore(Algebra/Homology): unexpose HomologicalComplexUpToQuasiIso.Qh #43103

[github-actions]

PR summary bfea792fdf

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference
Mathlib.Algebra.Homology.DerivedCategory.Ext.MapAdjunction (new file)	1455

---

Declarations diff (regex)

+ comp_mapExactFunctor
+ extEquiv
+ extEquiv_mk₀
+ extEquiv_mk₀_counit_app
+ extEquiv_naturality_left
+ extEquiv_naturality_left₀
+ extEquiv_naturality_right
+ extEquiv_naturality_right₀
+ extEquiv_symm_mk₀
+ extEquiv_symm_mk₀_unit_app
+ extEquiv_symm_naturality_left
+ extEquiv_symm_naturality_left₀
+ extEquiv_symm_naturality_right
+ extEquiv_symm_naturality_right₀
+ extLinearEquiv
+ id_mapExactFunctor
+ mapExactFunctor_comp_mk₀_natTransApp

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 -- pending)

Computed after the build finishes.

---

No changes to strong technical debt.

Increase in weak tech debt: (relative, absolute) = (1.00, 0.00)

Current number	Change	Type (weak)
4967	1	exposed public sections

Current commit bfea792fdf
Reference commit dbb8420388

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).

[mathlib-dependent-issues]

This PR/issue depends on:

• feat(Algebra/Homology): pseudofunctorial behaviour of Functor.mapDerivedCategory #43089
• chore(Algebra/Homology): unexpose HomologicalComplexUpToQuasiIso.Qh #43103
  By Dependent Issues (🤖). Happy coding!