gitstats: Add a description about the matcher module

This briefly lists the most useful functions it exports,
it should later be made to include a more detailed
description of what metrics the user should expect this
subcommand to contain.

diff --git a/doc/matcher.txt b/doc/matcher.txt
new file mode 100644 (file)
index 0000000..682ffbb
--- /dev/null
+++ b/doc/matcher.txt
@@ -0,0 +1,19 @@
+syntax: stats.py matcher <options>
+
+The purpose of the matcher module is to compare hunks
+within one diff to one another, and determine whether there
+is any code being moved around.
+
+Currently the available metrics in the index module are the
+following:
+* Try to find a match between the hunks in one diff, so
+  that code moves can be detected. This makes use of the
+  'diff size calculation' described below.
+
+It also defines the following auxillery functions:
+* Calculate the size of a diff, only counting the amount
+  of lines added, and the amount of lines deleted. This can
+  be used to determine a best 'interdiff' (the shortest one
+  is the best one), when searching for two hunks that are
+  moved around.
+