Drew Crawford [off-list ref] writes:
I noticed today that if you leave off the branch name from git subtree like so:
$ git subtree add --prefix somewhere -m "adding CDH as subtree" path/to/repo
warning: read-tree: emptying the index with no arguments is deprecated; use --empty
fatal: just how do you expect me to merge 0 trees?
The error message is not particularly helpful (and seems to actually be in read-subtree?) The solution in my case was to add the branch name on the end of the command.
Ideally it would be better to emit an error-message from a script higher up the calling chain that would be more descriptive about the problem (such as suggesting no branch is specified).--
Good idea. I'll code it up.
-David