RFR: 32: GitRepository::show does not work with executable files

[Erik Duveblad via github.com]

Hi all,

this small patch fixes a bug that `GitRepository::show` did not work with executable files. I also added unit test for the scenario.

Testing: passes `sh gradlew test` on Linux x86-64

Thanks,
Erik

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Commits:
 - df788d23:	32: GitRepository::show does not work with executable files

Pull request:
http://git.openjdk.java.net/skara/pull/15

Webrev:
https://openjdk.github.io/cr/skara/15/webrev.00

Patch:
http://git.openjdk.java.net/skara/pull/15.diff

Fetch command:
git fetch https://github.com/openjdk/skara.git df788d23:pr/15