Add git and gpg configs

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

users/common/configs/gpg-agent/default.nix

@@ -0,0 +1,45 @@
+{ pkgs, ... }:
+
+{
+  services.gpg-agent = {
+    enable = true;
+    defaultCacheTtl = 31536000;
+    maxCacheTtl = 31536000;
+  };
+
+  systemd.user.services.gpg-agent-import = {
+    Unit = {
+      Description = "Auto-import GPG keys";
+      After = [ "gpg-agent.socket" "sops-nix.service" ];
+    };
+
+    Service = {
+      Type = "oneshot";
+      ExecStart = pkgs.writeScript "import-gpg-keys" ''
+        #!${pkgs.runtimeShell}
+
+        find "$HOME"/.gnupg -type f -exec chmod 600 {} \;
+        find "$HOME"/.gnupg -type d -exec chmod 700 {} \;
+
+        for keyfile in "$HOME"/.config/sops-nix/secrets/gpg-agent/*.key; do
+          passfile="''${keyfile%.key}.pass"
+
+          if [ -f "$passfile" ]; then
+            gpg --batch --yes --pinentry-mode loopback --passphrase-file "$passfile" --import "$keyfile"
+          else
+            gpg --batch --yes --import "$keyfile"
+          fi
+
+          gpg --with-colons --import-options show-only --import "$keyfile" | grep '^fpr' | cut -d: -f10 | while read -r KEY_ID; do
+            echo "$KEY_ID:6:" >> "$HOME"/.gnupg/otrust.txt
+          done
+        done
+
+        gpg --import-ownertrust "$HOME"/.gnupg/otrust.txt
+        rm "$HOME"/.gnupg/otrust.txt
+      '';
+    };
+
+    Install = { WantedBy = [ "default.target" ]; };
+  };
+}