tests: raise a better error when patterns are wrongly formatted It is fairly easy to make mistakes when merging conflict in the pattern file. A common mistake is to forget adding an extra trailing comma changing the length of the tuple. We now detect such error and raise a better error message that helps to find it.

Ancestors of 5
4 2 0 
Ancestors of 6 and 5
3 4 2 1 0 
Ancestors of 5 and 4
4 2 0 
Ancestors of 7, stop at 6
6 
Ancestors of 7, including revs
7 6 5 3 4 2 1 0 
Ancestors of 7, 5 and 3, including revs
7 5 3 6 4 2 1 0 

Descendants of 5
7 8 
Descendants of 5 and 3
6 7 8 
Descendants of 5 and 4
5 7 8