Spike of performance inprovment when fetching base configuration.

This is just spike to see if it's possible to fetch the base configuraton
a little bit faster.

Author: orjan

src/GitVersionCore/BranchConfigurationCalculator.cs

@@ -56,7 +56,9 @@ static KeyValuePair<string, BranchConfig> InheritBranchConfiguration(bool onlyEv
                     excludedInheritBranches = repository.Branches.Where(b =>
                     {
                         var branchConfig = LookupBranchConfiguration(config, b);
-                        return branchConfig.Length == 1 && branchConfig[0].Value.Increment == IncrementStrategy.Inherit;
+                        // TODO: I don't this there's the branch if no branchConfig exists?
+                        // TODO: we should probably warn if we find more than one branch config?
+                        return (branchConfig.Length != 1) || (branchConfig.Length == 1 && branchConfig[0].Value.Increment == IncrementStrategy.Inherit);
                     }).ToList();
                 }
                 excludedBranches.ToList().ForEach(excludedInheritBranches.Add);
@@ -66,14 +68,14 @@ static KeyValuePair<string, BranchConfig> InheritBranchConfiguration(bool onlyEv
                 List<Branch> possibleParents;
                 if (branchPoint == null)
                 {
-                    possibleParents = currentCommit.GetBranchesContainingCommit(repository, true).Except(excludedInheritBranches).ToList();
+                    possibleParents = currentCommit.GetBranchesContainingCommit(repository, true, excludedInheritBranches).ToList();
                 }
                 else
                 {
-                    var branches = branchPoint.GetBranchesContainingCommit(repository, true).Except(excludedInheritBranches).ToList();
+                    var branches = branchPoint.GetBranchesContainingCommit(repository, true, excludedInheritBranches).ToList();
                     if (branches.Count > 1)
                     {
-                        var currentTipBranches = currentCommit.GetBranchesContainingCommit(repository, true).Except(excludedInheritBranches).ToList();
+                        var currentTipBranches = currentCommit.GetBranchesContainingCommit(repository, true, excludedInheritBranches).ToList();
                         possibleParents = branches.Except(currentTipBranches).ToList();
                     }
                     else

src/GitVersionCore/GitVersionContext.cs

@@ -48,7 +48,7 @@ public GitVersionContext(IRepository repository, Branch currentBranch, Config co
 
             if (currentBranch.IsDetachedHead())
             {
-                CurrentBranch = CurrentCommit.GetBranchesContainingCommit(repository, OnlyEvaluateTrackedBranches).OnlyOrDefault() ?? currentBranch;
+                CurrentBranch = CurrentCommit.GetBranchesContainingCommit(repository, OnlyEvaluateTrackedBranches, new Branch[] {}).OnlyOrDefault() ?? currentBranch;
             }
             else
             {

src/GitVersionCore/LibGitExtensions.cs

@@ -68,10 +68,15 @@ static bool IsSameBranch(Branch branch, Branch b)
             return (b.IsRemote ? b.Name.Replace(b.Remote.Name + "/", string.Empty) : b.Name) != branch.Name;
         }
 
-        public static IEnumerable<Branch> GetBranchesContainingCommit(this Commit commit, IRepository repository, bool onlyTrackedBranches)
+        // TODO: we should probably pass a ISet<Branch> here
+        public static IEnumerable<Branch> GetBranchesContainingCommit(this Commit commit, IRepository repository, bool onlyTrackedBranches, IList<Branch> excludedInheritBranches)
         {
+            var excludedSet = new HashSet<Branch>(excludedInheritBranches);
+            var remainingBranches = repository.Branches.Where(b => !excludedSet.Contains(b)).ToList();
+
+
             var directBranchHasBeenFound = false;
-            foreach (var branch in repository.Branches)
+            foreach (var branch in remainingBranches)
             {
                 if (branch.Tip.Sha != commit.Sha || (onlyTrackedBranches && !branch.IsTracking))
                 {
@@ -87,8 +92,9 @@ public static IEnumerable<Branch> GetBranchesContainingCommit(this Commit commit
                 yield break;
             }
 
-            foreach (var branch in repository.Branches.Where(b => (onlyTrackedBranches && !b.IsTracking)))
+            foreach (var branch in remainingBranches.Where(b => (onlyTrackedBranches && !b.IsTracking)))
             {
+                // NOTE: is it better to compare Sha instead of commit?
                 var commits = repository.Commits.QueryBy(new CommitFilter { Since = branch }).Where(c => c.Sha == commit.Sha);
 
                 if (!commits.Any())