Fix the command name.

[Sormany Silva Dantas]

$ tst checkout
Not a tst directory and no object specified

---
Use `tst checkout <name>` to checkout object <name> in its directory
Use `tst checkout <name> <dir>` to checkout object <name> in <dir>
Use `tst ls` to list all objects available
You can use either a <name> or an integer identifier

Use tst ls to list all objects available
but it should be
Use tst list to list all objects available

[Sormany Silva Dantas]

Problem solved.