Issue 7059 - Modify fldiff so it can handle multiple files

README.md

Index: README.md
===================================================================
--- a/README.md
+++ b/README.md
@@ -94,14 +94,18 @@
 filter lists (e.g. network data, memory usage, battery consumption, etc.), allowing 
 clients to update their lists more frequently using less resources.

[Vasily Kuznetsov, 2018/10/24 11:30:08]

We normally try to limit line length to <80 characters in the documentation
files. It's not really documented anywhere but it's pretty consistent and it's
easier to read such files so I would recommend to format this section this way.

 
-Python-abp contains a script that produces the diff between two versions of a
-filter list called `fldiff`:
+Python-abp contains a script called `fldiff` that will find the diff between the lastest

[Vasily Kuznetsov, 2018/10/24 11:30:08]

Nit: should it be "latest"?

+filter list, and any number of previous filter lists:
 
-    $ fldiff base.txt latest.txt output.txt
+    $ fldiff -o diffs/easylist -l last-easylist.txt archive/*
+where `-o diffs/easylist` is the (optional) directory where the diffs should be written,
+`-l last-easylist.txt` is the most recent version of the filter list, and
+`archive/*` is the directory where all the the archived filter lists are. When called
+like this, the shell should automatically expand the `archive/*` directory, giving the script
+each of the files separately.
 
-This will produce a diff that shows how a client may get from `base.txt` to
-`latest.txt`, and write the output to `output.txt`. The output argument is
-optional. If ommitted, the data will be written to `stdout`.
+The output of each `list[version].txt` will be written to `diffs/diff[version].txt`.
+The output argument is optional. If ommitted, the data will be written to `stdout`.
 
 The script produces three types of lines, as specified in the [technical specification][5]:
 * Special comments of the form `! <name>:[ <value>]`