add docs and change name of env var

README.md

@@ -184,12 +184,11 @@ By default, `shallow-backup` backs these up.
 
 ### Configuration
 
-If you'd like to modify which files are backed up, you have to edit the `JSON` config file, located at `~/.config/shallow-backup.json`. There are two ways to do this.
+If you'd like to modify which files are backed up, you can edit the `JSON` config file. This file is looked for in the following locations, in this order:
 
-1. Select the appropriate option in the CLI and follow the prompts.
-2. Open the file in a text editor and make your changes.
-
-Editing the file in a text editor will give you more control and be faster.
+1. `$SHALLOW_BACKUP_CONFIG_DIR/shallow-backup.json`
+2. `$XDG_CONFIG_HOME/shallow-backup.json`
+3. `~/.config/shallow-backup.json`
 
 #### Conditional Backup and Reinstallation
 

shallow_backup/config.py

@@ -11,8 +11,8 @@
 
 
 def get_xdg_config_path() -> str:
-    """Returns path to $XDG_CONFIG_HOME, or ~/.config, if it doesn't exist."""
-    return environ.get("SHALLOW_BACKUP_HOME") or environ.get("XDG_CONFIG_HOME") or path.join(path.expanduser("~"), ".config")
+    """Returns path to $SHALLOW_BACKUP_CONFIG_DIR (if set), $XDG_CONFIG_HOME, or ~/.config if none of those exist."""
+    return environ.get("SHALLOW_BACKUP_CONFIG_DIR") or environ.get("XDG_CONFIG_HOME") or path.join(path.expanduser("~"), ".config")
 
 
 @lru_cache(maxsize=1)