Expand-Diff

The script is designed for diff and patch files created by git. It expands
the specified diff file into directories "a" and "b" (original and changes)
with pieces of files provided by the diff.

Then you can use your diff tool of choice in order to compare the
directories "a" and "b", i.e. to visualize the original diff file.

Diff file lines are processed as:

--- /dev/null - "a" is missing
+++ /dev/null - "b" is missing
--- a/...     - "a" file path
+++ b/...     - "b" file path
@@...         - chunk header
...          - common line
-...          - "a" line
+...          - "b" line

Other lines are ignored.