chore: add example to README

README.md

@@ -15,14 +15,17 @@ go get github.com/smlx/ccv
 
 ## Use it
 
+```
+# add an incremented tag if necessary
+if [ -z $(git tag -l $(ccv)) ]; then
+	git tag $(ccv)
+fi
+```
+
 `ccv` takes no arguments or options\*.
 
 \* Yet!
 
-```
-git tag $(ccv)
-```
-
 ## Prior art
 
 * [caarlos0/svu](https://github.com/caarlos0/svu) does pretty much the same thing, but it has more features and shells out to git. `ccv` uses [go-git/go-git](https://github.com/go-git/go-git) instead.