Clarify explanatory text for .gitignore

Author: evanderiel

book/02-git-basics/sections/recording-changes.asc

@@ -242,7 +242,7 @@ Here is another example `.gitignore` file:
 # only ignore the TODO file in the current directory, not subdir/TODO
 /TODO
 
-# ignore all files in the build/ directory
+# ignore all files in any directory named build
 build/
 
 # ignore doc/notes.txt, but not doc/server/arch.txt