Make repository a nix flake

Make git-email.el a nix flake for an easier installation process for
Nix users.  It currently exposes two packages:

- git-email-full -- This includes all the optional libraries
- git-email -- This only includes the core `git-email.el` library

They both get the source from directory from the git repository,
meaning they will get updates as soon as a commit is made.

* default.nix: Add file.
* flake.lock: Add file.
* flake.nix: Add file.

1 files changed, 29 insertions, 0 deletions

diff --git a/default.nix b/default.nix
new file mode 100644
index 0000000..9fa551a
--- /dev/null
+++ b/default.nix
@@ -0,0 +1,29 @@
+{ lib, nix-gitignore, emacsPackages }:
+let
+  inherit (emacsPackages) trivialBuild;
+  flakeRoot = toString ../.;
+in
+lib.recurseIntoAttrs rec {
+
+  git-email-full = trivialBuild rec {
+    pname = "git-email-full";
+    version = "git";
+    src = nix-gitignore.gitignoreSource (flakeRoot + ".gitignore") ./.;
+    packageRequires = with emacsPackages; [
+      magit
+      transient
+      notmuch
+    ];
+  };
+
+  git-email = trivialBuild rec {
+    pname = "git-email";
+    version = "git";
+    src = builtins.filterSource
+      (path: type:
+        baseNameOf path != "git-email-magit.el" &&
+        baseNameOf path != "git-email-notmuch.el" &&
+        baseNameOf path != "git-email-gnus.el"
+      ) ./.;
+  };
+}