A regression that was introduced with d79d20d.

This reverts commit 01f09888208341876d1480bd22dc8f4107c100f1.

The whitespace handling and trailer selection isn't very trivial or good
documented. It therefore seemed easier and less error prone to just call
git to parse the message for the trailers section and remove superfluos
whitespaces.

With the command `git interpret-trailers` git provides a way to interact
with trailer lines in the commit messages that look similar to RFC 822
e-mail headers (see: https://git-scm.com/docs/git-interpret-trailers).
The new property returns those parsed trailer lines from the message as
dictionary.

Use NUL character instead of semicolon to extract meta and path. Avoid errors in during git diff when dealing with filenames containing semicolons

This isn't needed as git will replace this file atomicially,
hence we always see a fully written file when reading.

Only when writing we need to obtain a lock.