From: Chris Torek <chris.torek@gmail.com>

'git mv' has always complained about renaming a conflicted
file, as it cannot handle multiple index entries for one file.
However, the error message it uses has been the same as the
one for an untracked file:

    fatal: not under version control, src=...

which is patently wrong.  Distinguish the two cases and
add a test to make sure we produce the correct message.

Signed-off-by: Chris Torek <chris.torek@gmail.com>

Submitted-As: https://lore.kernel.org/git/pull.678.v2.git.1595225873014.gitgitgadget@gmail.com
In-Reply-To: https://lore.kernel.org/git/pull.678.git.1595028293855.gitgitgadget@gmail.com