what does "a/:b/" stand for?

[Timmie]

On page:
http://developer.ubuntu.com/packaging/html/udd-patchsys.html

I have difficulties to understand, what in $ bzr diff -p "a/:b/" > ../bug-12345.patch
the part "a/:b/" stands for.

Also, please explain: how do I issue the revision diff (e.g. bzr diff -r1306 setup.py) in the correct quilt format

[Andrew Starr-Bochicchio (andrewsomething)]

There's a hint there, but no it is not entirely clear. This should get cleaned up a bit.

From 'bzr help diff'

  -p ARG, --prefix=ARG Set prefixes added to old and new filenames, as two
                        values separated by a colon. (eg "old/:new/").

Here's an example:

$ bzr diff
=== modified file 'bar'
--- bar 2012-07-30 14:43:52 +0000
+++ bar 2012-07-30 14:44:09 +0000
@@ -1,1 +1,1 @@
-Some text.
+Different text.

$ bzr diff -p "a/:b/"
=== modified file 'bar'
--- a/bar 2012-07-30 14:43:52 +0000
+++ b/bar 2012-07-30 14:44:09 +0000
@@ -1,1 +1,1 @@
-Some text.
+Different text.

$ bzr diff -p "old/:new/"
=== modified file 'bar'
--- old/bar 2012-07-30 14:43:52 +0000
+++ new/bar 2012-07-30 14:44:09 +0000
@@ -1,1 +1,1 @@
-Some text.
+Different text.

See what changed?