fix incorrect warning when walking on a particular rev
when a directory was given instead of a file it reported
incorrectly 'No such file or directory in rev <rev>'
we test if the file is a prefix directory
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Should display 'First commit message'
description:
First commit message
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Should display 'Second commit message'
description:
Second commit message
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Should display 'Third commit message\n This is the 3rd log message'
description:
Third commit message
This is the 3rd log message
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Should display 'Fifth commit message\n This is the 5th log message'
description:
Fifth commit message