Faster merge workflow: Support auto-stashing for merging in the same way it is already supported for pulling

(Note: relates to this request, which deals with safely aborting merges)

When you pull from the remote origin into a repot that has local changes, SmartGit has a great feature where it will auto-stash before the pull, and auto-apply the stash after pulling. If conflicts occur after pulling, the user must manually apply the auto-saved stash after resolving the conflicts.

This feature is a huge time saver, and prevents loss of work as well.

This request is to implement the same feature for merging into a branch with local changes. 

Currently I have to do this:

Best case:

• Create a stash (because I don't know if the merge will generate conflicts or not until I try)
• Merge (no conflicts)
• Apply the stash (no conflicts)
• Drop the stash

Worst case:

• Create a stash
• Merge
• Resolve merge conflicts
• Manually apply the stash
• Resolve conflicts from applying the stash
• Drop the stash

What I would like is for SmartGit to perform the auto-stash / auto-unstash for me before/after merging. The resulting workflow would be simplified:

Best case:

• Merge (SmartGit does auto-stash/un-stash, no conflicts at all from merge or unstash, SmartGit auto-drops the stash)

Worst case:

• Merge (SmartGit auto-stashes)
• Resolve merge conflicts and continue the merge 
• Manually apply the stash
• (Possibly) Resolve conflicts from the auto-unstash
• Drop the stash

As you can see, this reduces the common-case (clean merge, clean unstash) from 4 steps to 1.

In the middle case (conflicts only upon merge or unstash, but not both) it reduces it from 6 steps to 4.

In the worst case (conflicts on both merge and un-stash) it reduces it from 6 steps to 5.