.version file is not created for the current project with --no-skip-current

* carthage install method: [ ] .pkg, [ ] homebrew, [ ] source
* `which carthage`: `/usr/local/bin/carthage`
* `carthage version`: 0.31.2
* `xcodebuild -version`: `Build version 9F1027a`
* Are you using `--no-build`? No
* Are you using `--no-use-binaries`? No
* Are you using `--use-submodules`? No
* Are you using `--cache-builds`? Yes
* Are you using `--new-resolver`? Yes

**Cartfile**
n/a
**Carthage Output**
n/a

**Actual outcome**

When running `carthage build --no-skip-current` .version files are generated for the dependencies but not for the current project

**Expected outcome**
.version file is generated for the current project

**Implementation suggestion**

To extract the `version` all that needs to be done is:
```
git describe --exact-match `git rev-parse HEAD`
```

In case of no match just take the `HEAD` commitish