Jacob Helwig mentions in his answer that:
It looks like rev-parse is being used without sufficient error checking before-hand
Commit 62f162f from Jeff King (peff) should improve the robustness of git rev-parse in Git 1.9/2.0 (Q1 2014) (in addition of commit 1418567):
For cases where we do not match (e.g., "
doesnotexist..HEAD"), we would then want to try to treat the argument as a filename.
try_difference()gets this right, and always unmunges in this case.
However,try_parent_shorthand()never unmunges, leading to incorrect error messages, or even incorrect results:
$ git rev-parse foobar^@
foobar
fatal: ambiguous argument 'foobar': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions, like this:
'git <command> [<revision>...] -- [<file>...]'