git: Add update script

pkgs/applications/version-management/git-and-tools/git/update.sh

@@ -0,0 +1,18 @@
+#!/usr/bin/env nix-shell
+#!nix-shell -i bash -p curl common-updater-scripts jq
+
+set -eu -o pipefail
+
+oldVersion="$(nix-instantiate --eval -E "with import ./. {}; git.version or (builtins.parseDrvName git.name).version" | tr -d '"')"
+latestTag="$(git ls-remote --tags --sort="v:refname" git://github.com/git/git.git | grep -v '\{\}' | grep -v '\-rc' | tail -1 | sed 's|^.*/v\(.*\)|\1|')"
+
+if [ ! "${oldVersion}" = "${latestTag}" ]; then
+  update-source-version git "${latestTag}"
+  nixpkgs="$(git rev-parse --show-toplevel)"
+  default_nix="$nixpkgs/pkgs/applications/version-management/git-and-tools/git/default.nix"
+  nix-build -A git
+  git add "${default_nix}"
+  git commit -m "git: ${oldVersion} -> ${latestTag}"
+else
+  echo "git is already up-to-date"
+fi