Find all merge in Ancestry Path

In Git, I can get all of need commits via

git log hash..master --ancestry-path --merges

Is there an equivalent to do this in LibGit2Sharp?

Solution

First some basics:

git log topic..master

var filter = new CommitFilter { 
    SortBy = CommitSortStrategies.Time,
    Since = master,
    Until = topic,
};
var commitList = repo.Commits.QueryBy (filter);

git log topic..master --merges

var filter = new CommitFilter { 
    SortBy = CommitSortStrategies.Time,
    Since = master,
    Until = topic,
};
var commitList = repo.Commits.QueryBy (filter);
var mergeList = commitList.Where (p => p.Parents.Count () >= 2);

Now to your question:

git log topic..master --ancestry-path --merges

ancestry-path =

       When given a range of commits to display (e.g.  commit1..commit2 or
       commit2 ^commit1), only display commits that exist directly on the
       ancestry chain between the commit1 and commit2, i.e. commits that
       are both descendants of commit1, and ancestors of commit2.

The -merges are easy once we have the ancestry path as we can filter the commits that have more then one parent. Getting the ancestry path requires some coding ;-)

Since the ICommitLog that is returned from commitList in the first example above contains a DAG (Directed Acyclic Graph) via the .Parents property, we need to walk the graph and get "all the simple paths” via a depth-first search to find all non-cyclical paths. Once you have a list of all the simple paths just filter it by which commits have >=2 parents.

Note: I have done this in a few C# projects and even simple ones like calc'ing the pull-request related to a particular commit uses this depth-first ancestry. I tend to stay away from Linq to do this as I have huge commit lists (100k+ nodes between the start to end nodes within just the sub-DAG that I searching) and also avoid recursive methods due to stack size but your use-case may/will differ. If you get stuck at this point, post another question with your algorithm/code issue.