Merge branch 'ah/log-no-graph'

"git log --graph --graph" used to leak a graph structure, and there was no way to countermand "--graph" that appear earlier on the command line. A "--no-graph" option has been added and resource leakage has been plugged. * ah/log-no-graph: log: add a --no-graph option log: fix memory leak if --graph is passed multiple times