docs: both user & /opt in ReadMe

.README.md

@@ -34,6 +34,13 @@ dotfiles checkout 2>&1 | egrep "\s+" | awk {'print $1'} |
 dotfiles checkout
 ```
 
+When the `fetch` configuration is not set, insert the following line in
+`.dotfiles/config`:
+
+```config
+    fetch = +refs/heads/*:refs/remotes/origin/*
+```
+
 ## Install into `/etc/skel`
 
 ```sh
@@ -82,6 +89,10 @@ lazygit --git-dir=$HOME/.dotfiles --work-tree=$HOME
 
 ## Generic Tips
 
+### Desktop Files
+
+See <https://specifications.freedesktop.org/desktop-entry-spec/latest/>
+
 ### Github Patches
 
 From [stackoverflow](https://stackoverflow.com/questions/28484186/apply-github-commit-pull-request-as-a-patch).
@@ -103,12 +114,8 @@ dpkg-divert --divert /usr/share/zsh/vendor-completions/_rg --rename /usr/share/z
 
 ## Fonts
 
-- [How to install and manage fonts on Linux](https://linuxconfig.org/how-to-install-and-manage-fonts-on-linux)
-  - `mv folder ~/.fonts`
-  - `fc-cache -fv ~/.fonts`
-
 - [JetBrains Mono](https://www.jetbrains.com/lp/mono/)
-  - Install the files **without “NL”** (i.e No Ligatures) in their names
+  - Install the files **without** “NL” (No Ligatures) in their names
 
 - [Nerd Fonts](https://www.nerdfonts.com/)
   - [Download](https://github.com/ryanoasis/nerd-fonts/tags)
@@ -117,18 +124,66 @@ dpkg-divert --divert /usr/share/zsh/vendor-completions/_rg --rename /usr/share/z
   - [Cheat Sheet](https://www.nerdfonts.com/cheat-sheet)
   - <https://raw.githubusercontent.com/ryanoasis/nerd-fonts/master/bin/scripts/test-fonts.sh>
 
+### in $HOME/.fonts
+
+```sh
+mv folder ~/.fonts
+fc-cache -fv ~/.fonts
+```
+
+See also [How to install and manage fonts on Linux](https://linuxconfig.org/how-to-install-and-manage-fonts-on-linux).
+
+### in /opt/fonts
+
+`/etc/fonts/conf.d/00-opt.conf`:
+
+```xml
+<?xml version="1.0"?><!DOCTYPE fontconfig SYSTEM "fonts.dtd">
+<fontconfig>
+<dir>/opt/fonts</dir>
+</fontconfig>
+```
+
+```sh
+sudo mv folder /opt/fonts
+fc-cache -fv /opt/fonts
+```
+
 ## kitty
 
 - <https://sw.kovidgoyal.net/kitty/binary/>
-- Install `JetBrains Mono` (without NF) & `NerdFontsSymbolsOnly` fonts.
+
+### Dependencies
+
+- `JetBrains Mono` (without NL)
+- `NerdFontsSymbolsOnly`
   - Note: outside of kitty, it may be interesting to also install
-    _JetBrains Mono_ **with** _NF_.
+    _JetBrains Mono_ **with** _NL_.
 
 ```sh
 sudo apt install kitty-terminfo
-(kitty --version && curl https://sw.kovidgoyal.net/kitty/changelog/ | html2text) | less
+```
 
+### Install
+
+```sh
+# Show installed version, debian package & changelog
+(ls =kitty;
+ kitty --version;
+ apt show kitty;
+ curl https://sw.kovidgoyal.net/kitty/changelog/ | html2text) | less
+
+# Debian package
+sudo apt install kitty
+
+# In $HOME
 sh ~/.config/kitty/installer.sh
+
+# In /opt/kitty.app
+sudo sh ~/.config/kitty/installer.sh launch=n dest=/opt
+sudo update-alternatives \
+  --install /usr/bin/x-terminal-emulator \
+  x-terminal-emulator /opt/kitty.app/bin/kitty 99
 ```
 
 **Note**:
@@ -165,6 +220,7 @@ LOCATION=$(curl -s $URI/releases/latest \
   | sed 's/,$//'       \
   | sed 's/"//g')
 echo $LOCATION
+
 wget $LOCATION
 tar xf *.tar.gz(om[1])
 ```
@@ -195,6 +251,9 @@ commit=, build date=, build source=unknown, version=unversioned, os=linux, arch=
 ```sh
 mkdir -p $HOME/.local/bin
 cd $HOME/.local/bin
+# ---
+mkdir -p /opt/neovim/bin
+cd /opt/neovim/bin
 
 curl -LO https://github.com/neovim/neovim/releases/download/nightly/nvim.appimage
 chmod u+x nvim.appimage
@@ -230,28 +289,32 @@ flatpak install flathub io.neovim.nvim
 - Trash:
   - `trash-cli` is a much better CLI-only solution!
     Compare the outputs of `trash-cli` and `gio trash --list`…
+    <https://github.com/andreafrancia/trash-cli>
   - For `gio trash`, packages `libglib2.0` & `gvfs` are recommended.
 
 ### From source
 
 ```sh
- # From release
+# From release
 URI=https://github.com/jarun/nnn
 xdg-open $URI/releases/latest
 ARCHIVE=$(echo $HOME/Downloads/*.gz(om[1])) && echo $ARCHIVE
 tar xf $ARCHIVE
 
- # From repository
+# From repository
 git clone https://github.com/jarun/nnn.git
 
  # Compile
 cd nnn*(om[1])
 make clean
-sudo make O_GITSTATUS=1 O_NAMEFIRST=1 O_NERD=1 install
+
+sudo make                 O_GITSTATUS=1 O_NAMEFIRST=1 O_NERD=1 install
+sudo make PREFIX=/opt/nnn O_GITSTATUS=1 O_NAMEFIRST=1 O_NERD=1 install
+
 sudo cp -v misc/auto-completion/zsh/* /usr/local/share/zsh/site-functions
 sudo chmod a+r /usr/local/share/zsh/site-functions/*
 
- # Plugins
+# Plugins
 mv -v ~/.config/nnn/plugins plugins_$(stat -c %Y ~/.config/nnn/plugins)
 mkdir -p ~/.config/nnn
 cp -av plugins ~/.config/nnn