Store empty (default) branch in branch cache, too.
Operations on this branch don't work otherwise.
Reading branches.cache had to be adjusted to allow an empty label.
Adjusted reading of the cache tip for symmetry, no functional change here.
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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