This used to work about a year ago. Now it doesn't:

git log --abbrev=6

The expected result would be all commit hashes abbreviated to 6 characters.

The actual result is now this error message:

fatal: ambiguous argument '6': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions, like this:
'git [...] -- [...]'

I have the impression that Git doesn't even know about that argument and tries to silently ignore its name but not the value.

Using Git 1.8.1.msysgit.1 on Windows 7.

Addition: Oh and it fails on other parameters, too. The entire command is:

git log --abbrev=6 --format=format:"----- Commit %%h on %%ci by %%an -----%%n%%n%%B"

If I just leave the abbrev part out, it still returns another error:

fatal: Invalid object name 'format'.