Add Difference Between wq and x as a vim til.

README.md

@@ -302,6 +302,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 - [Delete Every Other Line](vim/delete-every-other-line.md)
 - [Delete Lines That Match A Pattern](vim/delete-lines-that-match-a-pattern.md)
 - [Deleting Directories Of Files From netrw](vim/deleting-directories-of-files-from-netrw.md)
+- [Difference Between :wq and :x](vim/difference-between-wq-and-x.md)
 - [Display Word Count Stats](vim/display-word-count-stats.md)
 - [Edges Of The Selection](vim/edges-of-the-selection.md)
 - [End Of The Word](vim/end-of-the-word.md)

vim/difference-between-wq-and-x.md

@@ -0,0 +1,23 @@
+# Difference Between :wq and :x
+
+The `:wq` command is used in Vim to write and quit. The contents of the
+buffer are written to disk for the associated file and then the Vim session
+is terminated. So, what is the difference between this and the `:x` command.
+The Vim help files give the following description of the `:x` command:
+
+> Like ":wq", but write only when changes have been made.
+
+So, `:wq` writes the buffer to disk either way, whereas `:x` just exits if the
+buffer hasn't changed. Either way the contents of the resulting file are
+going to be the same. So what's the difference?
+
+Modification time.
+
+If you `:x` a buffer that hasn't changed, the modification time will be
+untouched because the file isn't *re-saved*. The `:wq` command will alter
+the modification time no matter what.
+
+This matters if the modification time is used by anything. For instance, a
+background process that monitors a directory for changed files based on
+modification times will get some false positives if you use `:wq` to
+liberally.