emacsPackages: factor out the functions from update-from-overlay

The functions are useful for other purposes too. So, let's put them on
`lib-update-scripts.sh`.

pkgs/applications/editors/emacs/elisp-packages/lib-update-scripts.sh

@@ -0,0 +1,40 @@
+#!/usr/bin/env bash
+
+# This script is a basic library that concentrates the main tasks of bulk updating:
+# - download from Emacs overlay
+# - test the packageset
+# - commit the changes
+
+SOURCE=${BASH_SOURCE[0]}
+# resolve $SOURCE until the file is no longer a symlink
+while [ -L "$SOURCE" ]; do
+    DIR=$( cd -P "$( dirname "$SOURCE" )" >/dev/null 2>&1 && pwd )
+    SOURCE=$(readlink "$SOURCE")
+    # if $SOURCE was a relative symlink, we need to resolve it relative to the
+    # path where the symlink file was located
+    [[ $SOURCE != /* ]] && SOURCE=$DIR/$SOURCE
+done
+DIR=$( cd -P "$( dirname "$SOURCE" )" >/dev/null 2>&1 && pwd )
+
+download_change() {
+    local FILE_LOCATION="$1"
+
+    local BASEURL="https://raw.githubusercontent.com/nix-community/emacs-overlay/master/repos"
+
+    curl -s -O "${BASEURL}/${FILE_LOCATION}"
+}
+
+commit_change() {
+    local MESSAGE="$1"
+    local FILENAME="$2"
+    local FROM="$3"
+
+    git diff --exit-code "${FILENAME}" > /dev/null || \
+        git commit -m "${MESSAGE}: updated at $(date --iso) (from ${FROM})" -- "${FILENAME}"
+}
+
+test_packageset(){
+    local PKGSET="$1"
+
+    NIXPKGS_ALLOW_BROKEN=1 nix-instantiate --show-trace ${DIR}/../../../../../ -A "emacsPackages.$PKGSET"
+}

pkgs/applications/editors/emacs/elisp-packages/update-from-overlay

@@ -5,29 +5,7 @@ set -euxo pipefail
 # This script piggybacks on the automatic code generation done by the nix-community emacs overlay
 # You can use this to avoid running lengthy code generation jobs locally
 
-export NIXPKGS_ALLOW_BROKEN=1
-
-download_change() {
-    local FILE_LOCATION="$1"
-
-    local BASEURL="https://raw.githubusercontent.com/nix-community/emacs-overlay/master/repos"
-
-    curl -s -O "${BASEURL}/${FILE_LOCATION}"
-}
-
-commit_change() {
-    local MESSAGE="$1"
-    local FILENAME="$2"
-
-    git diff --exit-code "${FILENAME}" > /dev/null || \
-        git commit -m "${MESSAGE}: updated $(date --iso) (from overlay)" -- "${FILENAME}"
-}
-
-test_packageset(){
-    local PKGSET="$1"
-
-    nix-instantiate --show-trace ../../../../../ -A "emacs.pkgs.$PKGSET"
-}
+source ./lib-update-scripts.sh
 
 download_change "elpa/elpa-generated.nix"
 download_change "elpa/elpa-devel-generated.nix"
@@ -42,8 +20,8 @@ test_packageset "elpaDevelPackages"
 test_packageset "melpaStablePackages"
 test_packageset "melpaPackages"
 
-commit_change "elpa-packages" "elpa-generated.nix"
-commit_change "elpa-devel-packages" "elpa-devel-generated.nix"
-commit_change "melpa-packages" "recipes-archive-melpa.json"
-commit_change "nongnu-packages" "nongnu-generated.nix"
-commit_change "nongnu-devel-packages" "nongnu-devel-generated.nix"
+commit_change "emacsPackages.elpaPackages" "elpa-generated.nix" "nix-community/emacs-overlay"
+commit_change "emacsPackages.elpaDevelPackages" "elpa-devel-generated.nix" "nix-community/emacs-overlay"
+commit_change "emacsPackages.melpaPackages" "recipes-archive-melpa.json" "nix-community/emacs-overlay"
+commit_change "emacsPackages.nongnuPackages" "nongnu-generated.nix" "nix-community/emacs-overlay"
+commit_change "emacsPackages.nongnuDevelPackages" "nongnu-devel-generated.nix" "nix-community/emacs-overlay"