documentation around 'command'

Author: colinta

FileDiffs.sublime-settings

@@ -10,6 +10,9 @@
 	// NOTE: Copy/paste example below or write your own command in: Package Settings --> FileDiffs --> Settings - User
 	// This file will be overwritten if the package is updated.
 
+	// The "command" argument is different depending on your system, for instance
+	// you might need to prefix /usr/local/bin, or use another explicit path.
+
 	// opendiff (FileMerge)
 	// "cmd": ["opendiff", "$file1", "$file2"]
 

README.md

@@ -39,7 +39,9 @@ Add External Diff Tool *(optional)*
 
 1. Preferences > Package Settings > FileDiffs > Settings - Default
 
-2. Uncomment one of the examples or write you own command to open external diff tool.
+2. Uncomment one of the examples or write your own command to open external diff tool.
+
+   This command *may* need to be a full path (e.g. `/usr/local/bin/ksdiff`), if the command isn't in your `PATH`.
 
 
 Commands