pkgs: add git-commit-last

Small helper which adds a command git commit-last, which,
as the name suggests, commits with the last commit message.
Useful when the commit fails for whatever reason
or something else happens during a commit.

pkgs/default.nix

@@ -10,5 +10,13 @@
       crane = inputs.crane.lib.${system};
       fenix = inputs'.fenix.packages;
     };
+
+    packages.git-commit-last = pkgs.writeShellApplication {
+      name = "git-commit-last";
+      text = ''
+        GITDIR="$(git rev-parse --git-dir)"
+        git commit -eF "$GITDIR/COMMIT_EDITMSG"
+      '';
+    };
   };
 }