adding nix configuration

.nix/config.nix

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+{
+  ## DO NOT CHANGE THIS
+  format = "1.0.0";
+  ## unless you made an automated or manual update
+  ## to another supported format.
+
+  ## The attribute to build, either from nixpkgs
+  ## of from the overlays located in `.nix/coq-overlays`
+  attribute = "algebra-tactics";
+
+  ## If you want to select a different attribute
+  ## to serve as a basis for nix-shell edit this
+  # shell-attribute = "{{nix_name}}";
+
+  ## Maybe the shortname of the library is different from
+  ## the name of the nixpkgs attribute, if so, set it here:
+  # pname = "{{shortname}}";
+
+  ## Lists the dependencies, phrased in terms of nix attributes.
+  ## No need to list Coq, it is already included.
+  ## These dependencies will systematically be added to the currently
+  ## known dependencies, if any more than Coq.
+  ## /!\ Remove this field as soon as the package is available on nixpkgs.
+  ## /!\ Manual overlays in `.nix/coq-overlays` should be preferred then.
+  # buildInputs = [ ];
+
+  ## Indicate the relative location of your _CoqProject
+  ## If not specified, it defaults to "_CoqProject"
+  # coqproject = "_CoqProject";
+
+  ## select an entry to build in the following `bundles` set
+  ## defaults to "default"
+  default-bundle = "8.13";
+
+  ## write one `bundles.name` attribute set per
+  ## alternative configuration, the can be used to
+  ## compute several ci jobs as well
+  bundles = {
+    "8.13" = {
+      coqPackages.coq.override.version = "8.13";
+    };
+  };
+
+  ## Cachix caches to use in CI
+  ## Below we list some standard ones
+  cachix.coq = {};
+  cachix.math-comp = {};
+  cachix.coq-community = {};
+
+  ## If you have write access to one of these caches you can
+  ## provide the auth token or signing key through a secret
+  ## variable on GitHub. Then, you should give the variable
+  ## name here. For instance, coq-community projects can use
+  ## the following line instead of the one above:
+  # cachix.coq-community.authToken = "CACHIX_AUTH_TOKEN";
+
+  ## Or if you have a signing key for a given Cachix cache:
+  # cachix.my-cache.signingKey = "CACHIX_SIGNING_KEY"
+
+  ## Note that here, CACHIX_AUTH_TOKEN and CACHIX_SIGNING_KEY
+  ## are the names of secret variables. They are set in
+  ## GitHub's web interface.
+}

.nix/coq-nix-toolbox.nix

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+"6bfe83b1a07fede9a0e6a7f60df554323051f8d2"

.nix/coq-overlays/algebra-tactics/default.nix

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+{ lib, mkCoqDerivation, coq, mathcomp-algebra,
+  coq-elpi, mathcomp-zify, version ? null }:
+
+with lib; mkCoqDerivation rec {
+  pname = "algebra-tactics";
+  owner = "math-comp";
+  inherit version;
+  defaultVersion = null;
+
+  propagatedBuildInputs = [ mathcomp-algebra coq-elpi mathcomp-zify ];
+
+  meta = {
+    description = "A Library for algebra tactics";
+    maintainers = with maintainers; [ cohencyril ];
+  };
+}

.nix/coq-overlays/mathcomp-zify/default.nix

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+{ lib, mkCoqDerivation, coq, mathcomp-algebra, version ? null }:
+
+with lib; mkCoqDerivation rec {
+  pname = "mathcomp-zify";
+  repo = "mczify";
+  owner = "math-comp";
+  inherit version;
+
+  defaultVersion = with versions;
+     switch [ coq.coq-version mathcomp-algebra.version ] [
+       { cases = [ (isEq "8.13") (isEq "1.12") ]; out = "1.0.0+1.12+8.13"; }
+     ] null;
+
+  release."1.0.0+1.12+8.13".sha256 = "1j533vx6lacr89bj1bf15l1a0s7rvrx4l00wyjv99aczkfbz6h6k";
+
+  propagatedBuildInputs = [ mathcomp-algebra ];
+
+  meta = {
+    description = "Micromega tactics for Mathematical Components";
+    maintainers = with maintainers; [ cohencyril ];
+  };
+}

default.nix

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+{ config ? {}, withEmacs ? false, print-env ? false, do-nothing ? false,
+  update-nixpkgs ? false, ci-matrix ? false,
+  override ? {}, ocaml-override ? {}, global-override ? {},
+  bundle ? null, job ? null, inNixShell ? null, src ? ./.,
+}@args:
+let auto = fetchGit {
+  url = "https://github.com/coq-community/coq-nix-toolbox.git";
+  ref = "master";
+# putting a ref here is strongly advised
+  rev = import .nix/coq-nix-toolbox.nix;
+};
+in
+import auto ({inherit src;} // args)