Re-organize the shells' initialization logic

- unify ~/.config/shell/aliases.sh and ~/.config/shell/utils.sh
  into a common ~/.config/shell/init.sh
- split the contents of ~/.config/shell/aliases.sh
  into the folder ~/.config/shell/aliases.d
- split the contents of ~/.config/shell/utils.sh
  into the folder ~/.config/shell/utils.d

.config/shell/utils.d/update.sh

@@ -0,0 +1,165 @@
+# This file defines the `update-machine` function that updates basically everything
+
+
+_command_exists() {
+    command -v "$1" 1>/dev/null 2>&1
+}
+
+_in_zsh() {
+    [ -n "$ZSH_VERSION" ]
+}
+
+
+
+_update_apt() {
+    _command_exists apt || return
+
+    echo 'Updating apt packages'
+    sudo apt update
+    sudo apt upgrade
+    sudo apt autoremove
+    sudo apt autoclean
+}
+
+_update_dnf() {
+    _command_exists dnf || return
+
+    echo 'Updating dnf packages'
+    sudo dnf upgrade --refresh
+    sudo dnf autoremove
+    sudo dnf clean all
+}
+
+_remove_old_snaps() {
+    sudo snap list --all | awk "/disabled/{print $1, $3}" |
+        while read snapname revision; do
+            sudo snap remove "$snapname" --revision="$revision"
+        done
+}
+
+
+
+# Update local git repositories (mostly ~/repos)
+_update_repositories() {
+    echo 'Updating repositories'
+
+    cwd=$(pwd)
+    cd $REPOS
+
+    # Otherwise the for-loop waites for manual input
+    # if it cd's into a folder with a ".env" file
+    ZSH_DOTENV_FILE='.do_not_run_dotenv'
+
+    for dir in */; do
+        cd "$REPOS/$dir" && echo "Fetching $REPOS/$dir"
+        git fetch --all --prune
+    done
+
+    ZSH_DOTENV_FILE='.env'
+
+    _command_exists pass && echo "Fetching $HOME/.password-store" && pass git pull
+    _update_dotfiles
+
+    cd $cwd
+}
+
+# Update the ~/.dotfiles repository
+_update_dotfiles() {
+    echo "Fetching $HOME/.dotfiles"
+    # The `dotfiles` alias is defined in ~/.bashrc at the end of the
+    # "Shell Utilities & Aliases" section and can NOT be used here
+    git --git-dir=$HOME/.dotfiles/ --work-tree=$HOME stash --quiet 
+    git --git-dir=$HOME/.dotfiles/ --work-tree=$HOME fetch --all --prune
+    git --git-dir=$HOME/.dotfiles/ --work-tree=$HOME pull --rebase --quiet
+    git --git-dir=$HOME/.dotfiles/ --work-tree=$HOME stash pop  # --quiet is ignored
+}
+
+
+
+_update_zsh() {
+    _in_zsh || return
+
+    echo 'Updating zsh'
+    _update_omz_fork
+    _update_zplug
+}
+
+_update_omz_fork() {
+    _command_exists omz || return
+
+    # In a nutshell, `omz update` pulls the latest origin/master
+    # from the original "oh-my-zsh" repo
+    omz update
+
+    cwd=$(pwd)
+    cd $ZSH
+
+    git checkout --quiet forked  # most likely already the case
+
+    # Keep our personal "oh-my-zsh" fork up-to-date
+    # See: https://gitlab.webartifex.biz/alexander/oh-my-zsh
+    git rebase --quiet master
+    git push --quiet fork forked
+    git push --quiet fork master
+
+    cd $cwd
+}
+
+_update_zplug() {
+    _command_exists zplug || return
+
+    zplug update
+    zplug install  # ensure newly added plugins in ~/.zshrc are never forgotten
+    zplug load
+}
+
+
+
+_update_python() {
+    echo 'Updating the Python tool chain'
+
+    if _command_exists pyenv; then
+        pyenv update
+        create-or-update-python-envs  # defined in ~/.config/shell/utils.d/python.sh
+    fi
+
+    if _command_exists zsh-pip-cache-packages; then
+        zsh-pip-clear-cache
+        zsh-pip-cache-packages
+    fi
+}
+
+
+
+_restore_gnome() {
+    for file in $HOME/.config/gnome-settings/*.ini; do
+        dconf load / < $file
+    done
+}
+
+
+
+run-private-scripts() {  # in the Nextcloud
+    if [ -d "$HOME/data/getraenkemarkt/shell" ]; then
+        for file in $HOME/data/getraenkemarkt/shell/*.sh; do
+            source $file
+        done
+    fi
+}
+
+
+
+update-machine() {
+    sudo --validate || return
+
+    _update_apt
+    _update_dnf
+    _command_exists flatpak && sudo flatpak update -y
+    _command_exists snap && sudo snap refresh && _remove_old_snaps
+    _update_repositories
+    _update_zsh
+    _update_python
+    _restore_gnome
+
+    sudo --reset-timestamp
+}