copies: add a config to limit the number of candidates to check in heuristics
The heuristics algorithm find possible candidates for move/copy and then check
whether they are actually a copy or move. In some cases, there can be lot of
candidates possible which can actually slow down the algorithm.
This patch introduces a config option
`experimental.copytrace.movecandidateslimit` using which one can limit the
candidates to check. The limit defaults to 100.
Thanks to Yuya for suggesting to skip copytracing for that file with a
warning.
Differential Revision: https://phab.mercurial-scm.org/D987
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