Add functionality to forcibly link items

This commit introduces an extended configuration syntax for linking
files and directories. Currently, this syntax allows for specifying
items to be forcibly linked, overwriting existing files or directories
if necessary.

The extended configuration syntax was proposed by Travers McInerney
<travers@mcinerney.me>.

1 files changed, 13 insertions, 1 deletions

diff --git a/README.md b/README.md
index 486fbd9..5c79337 100644
--- a/README.md
+++ b/README.md
@@ -91,6 +91,8 @@ have a defined ordering.
 ### Link
 
 Link commands specify how files and directories should be symbolically linked.
+If desired, items can be specified to be forcibly linked, overwriting existing
+files if necessary.
 
 #### Format
 
@@ -99,13 +101,23 @@ locations. Source locations are specified relative to the base directory (that
 is specified when running the installer). Source directory names should contain
 a trailing "/" character.
 
+Link commands support an (optional) extended configuration. In this type of
+configuration, instead of specifying source locations directly, targets are
+mapped to extended configuration dictionaries. These dictionaries map "path" to
+the source path, and specify "force" as true if the file or directory should be
+forcibly linked.
+
 ##### Example
 
 ```json
 {
     "link": {
         "~/.vimrc": "vimrc",
-        "~/.vim": "vim/"
+        "~/.vim": "vim/",
+        "~/.zshrc": {
+            "path": "zshrc",
+            "force": true
+        }
     }
 }
 ```