xbps-src: allow loading xbp-src.conf from XDG compliant dirs

README.md

@@ -165,7 +165,7 @@ If you don't want to waste your time building everything from scratch probably i
 
 The `etc/defaults.conf` file contains the possible settings that can be overridden
 through the `etc/conf` configuration file for the `xbps-src` utility; if that file
-does not exist, will try to read configuration settings from `~/.xbps-src.conf`.
+does not exist, will try to read configuration settings from `$XDG_CONFIG_HOME/xbps-src.conf`, `~/.config/xbps-src.conf`, `~/.xbps-src.conf`.
 
 If you want to customize default `CFLAGS`, `CXXFLAGS` and `LDFLAGS`, don't override
 those defined in `etc/defaults.conf`, set them on `etc/conf` instead i.e:

xbps-src

@@ -428,6 +428,10 @@ else
     elif [ -s $XBPS_DISTDIR/etc/conf ]; then
         # ... otherwise read generic user configuration...
         readonly XBPS_CONFIG_FILE=$XBPS_DISTDIR/etc/conf
+    elif [ -s $XDG_CONFIG_HOME/xbps-src.conf ]; then
+        readonly XBPS_CONFIG_FILE=$XDG_CONFIG_HOME/xbps-src.conf
+    elif [ -s $HOME/.config/xbps-src.conf ]; then
+        readonly XBPS_CONFIG_FILE=$HOME/.config/xbps-src.conf
     elif [ -s $HOME/.xbps-src.conf ]; then
         # ... fallback to ~/.xbps-src.conf otherwise.
         readonly XBPS_CONFIG_FILE=$HOME/.xbps-src.conf