More Recipes - Git Recipes - page 509

The above description unambiguously defines two versions of the file: the version
before we apply the changes and the version after we apply the changes. Using the
above output we can construct the file in two states: before and after the change.
The first two lines inform you that the output describes the changes of the file
named some-file-name . The version before the change can be retrieved by remov-
ing the lines that begin with + and writing the lines that begin with - without the lead-
ing dash. The above output describes the file before the change contained:
xxx
zzz
qqq
The version after the change can be retrieved by removing the lines that begin with
a dash and writing the lines that begin with + without the leading plus. The file after
the change looks like:
xxx
yyy
qqq
The special line:
@@ -a,b +c,d @@
defines two ranges of lines: a,b and c,d . The first range a,b describes the first
version of file. The second range, c,d describes the second version of file.
The range a,b indicates that this version before the change:
xxx
zzz
qqq
starts at line a and contains b lines.
The second range c,d indicates that this version after the change:
xxx
yyy
qqq