Solution merge stuck on 'Merging' when the source branch has conflicts with the target branch

[ewingjm]

Description
If the source branch specified on your solution merge has conflicts with the target branch, the solution merge will be stuck on a status of 'Merging' indefinitely.

Steps to reproduce

1. Create a branch from the target branch
2. Update a line in a file on the target branch
3. Update the same line in the branch created from the target branch
4. Create a solution merge and provide the branch created in step 1 as the source branch
5. Approve the solution merge
6. Observe that the solution merge is stuck in a status of 'Merging' indefinitely

Expected behaviour
The fact that there are merge conflicts with the target branch should be fed back to the solution merge.

Additional context
This is an issue in the Merge-SolutionMerge.ps1 script.