[firefox] Make it possible to stow firefox configuration

- Put ‘userChrome.css’ into the ‘src/’ directory and have stow ignore any such
  directory.

- Dynamically find the name of the default firefox profile.

- In case the firefox profile can't be found, output some messages stating such.

- Update the ‘userChrome.css’ as used by Firefox.

.stowrc

@@ -4,4 +4,5 @@
 --ignore .dir-locals.el
 --ignore PKGBUILD
 --ignore pkg.tar.xz
+--ignore src
 --no-folding

GNUmakefile

@@ -1,9 +1,11 @@
 MODULES=xmodmap emacs xdg shepherd dunst zsh mcron mbsync nyxt work \
-    herbstluftwm mpd polybar xbindkeys
+    herbstluftwm mpd polybar xbindkeys firefox
 
 STOW = stow
 EMACS = emacs
 SCHEME_IMPLEMENTATION = guile
+# Found this sed command here: https://stackoverflow.com/a/40778047
+FIREFOX_PROFILE := $(shell sed -nr "/^Name=default/ { :l /^Path=/ { s/[^=]*=[ ]*//; p; q; }; n; b l; }" ~/.mozilla/firefox/profiles.ini 2>/dev/null)
 
 .PRECIOUS: %.el
 
@@ -125,6 +127,21 @@ zsh: zsh/.profile zsh/.zshrc zsh/.zsh/functions/unzip.zwc \
 
 nyxt: nyxt/.config/nyxt/init.lisp
 
+## Firefox
+
+ifneq ($(FIREFOX_PROFILE),)
+firefox: firefox/.mozilla/firefox/$(FIREFOX_PROFILE)/chrome/userChrome.css
+
+firefox/.mozilla/firefox/$(FIREFOX_PROFILE)/chrome/userChrome.css: firefox/src/userChrome.css
+	mkdir -p $$(dirname $@)
+	cp $^ $@
+else
+firefox:
+	@echo "Error finding firefox default profile, can't make" >&2
+firefox-stow:
+	@echo "Error finding firefox default profile, can't stow" >&2
+endif
+
 ## Helper
 
 %.el: %.org

firefox/.gitignore

@@ -0,0 +1 @@
+.mozilla/

firefox/src/userChrome.css

@@ -1,4 +1,4 @@
-#tabbrowser-tabs, #tabbrowser-tabs > .tabbrowser-arrowscrollbox {
+#tabbrowser-tabs, #tabbrowser-arrowscrollbox {
   min-height: 0 !important;
 }