Updated Integration (markdown)

Integration.md

@@ -7,7 +7,7 @@ The easiest way is to just invoke `shellcheck`, either on a file or on stdin, an
 
 Here is an integration checklist. Each point is described further below:
 
-1. Pick a machine parsable output format: json, xml or gcc
+1. Pick a machine parsable output format: json, xml, gcc or diff
 1. Decide whether you want to manually specify a shell dialect
 1. Decide whether you want to follow `source`d files that are not specified as input
 1. Check `shellcheck`s exit code
@@ -123,6 +123,19 @@ myotherscript:2:2: error: You need a space after the [ and before the ]. [SC1035
 
 `line` and `column` start at 1, and assume a tab size of 1 (like `gcc` itself).
 
+### Unified Diff 
+
+While ShellCheck's fix suggestions can be found in the `json1` format, it's not well documented or easy to deal with. With `-f diff`, you can instead get standard unified diff output:
+
+```
+$ shellcheck -f diff file 
+--- a/file
++++ b/file
+@@ -1,2 +1,2 @@
+ #!/bin/sh
+-echo $1
++echo "$1"
+```
 
 ## Decide whether you want to specify a shell dialect