diff.txt

                                      diff
                                      ====

Unified format:

--- /path/to/old <tab> ''timestamp''
+++ /path/to/new <tab> ''timestamp''

       .- Line number 1 in the old file
      / .-- Sum of contextual lines and minuses in this hunk (1)
     / /
@@ -1,3 +1,8 @@
          \ \
           \ *-- Sum of contextual lines and pluses in this hunk (2)
            *- Line number 1 in the new file

- line: only present in old file
+ line: only present in new file

Differences:

+ This is an important        (2)
+ notice! It should           (2)
+ therefore be located at     (2)
+                             (2)
  This part of the        (1) (2)
- document has stayed the (1)
  same from version to    (1) (2)
+ the beginning of this       (2)
+ document!                   (2)

Multiple files comparison:

diff -uq --from-file file1 file2...filen

Compare directories:

diff -qr staging production