Nimble commands fail after `git init`
I've tried to run `nimble lock` on a directory which wasn't under version control, and I got this message:

```
    Error:  Sync file require current working directory to be under some supported type of version control.
     Hint:  Put package's working directory under version control.
```

(and this still created `nimble.lock` file, btw)

----

After that, I've run `git init`, and now `nimble lock` produces:

```
$ nimble lock
       Tip: 2 messages have been suppressed, use --verbose to show them.
tools.nim(62)            tryDoCmdEx

    Error:  Execution of 'git -C /home/miran/code/nim-lang/tests/myPackage rev-parse HEAD' failed with an exit code 128.
        ... Details: fatal: ambiguous argument 'HEAD': unknown revision or path not in the working tree.
        ... Use '--' to separate paths from revisions, like this:
        ... 'git <command> [<revision>...] -- [<file>...]'
        ... HEAD
```

The same error appears on _some_ other commands (e.g. `nimble check`, `nimble test`, or non-existing commands such as `nimble foobar`), but not on others (e.g. `nimble tasks` or `nimble list -i`).

-----

The issue is resolved after one makes a first commit. But then the original hint ("Put package's working directory under version control.") should be changed to reflect that just initializing git isn't enough.