Expose alternative strategies for resolving uncommitted changes

e.g. this:

```
There are uncommitted changes, which may cause problems or be lost when we push, pull, switch, or compare branches.
Do you want to proceed anyway?
1: Nope
2: Yes
3: No way
```
Could instead be:

```
What do you want to do?
1. Stash changes (restore with git_stash_pop())
2. Abort this operation
3. Try again, I've done something with git
4. Proceed anyway
```