Eagerly dispose of Remotes

This is a continuation of #1249. Since Remotes are now disposable we
should eagerly clean up their resources rather than wait for GC to call
the destructor.

Author: niik

LibGit2Sharp/Branch.cs

@@ -146,7 +146,10 @@ public virtual string UpstreamBranchCanonicalName
             {
                 if (IsRemote)
                 {
-                    return Remote.FetchSpecTransformToSource(CanonicalName);
+                    using (var remote = Remote)
+                    {
+                        return remote.FetchSpecTransformToSource(CanonicalName);
+                    }
                 }
 
                 return UpstreamBranchCanonicalNameFromLocalBranch();

LibGit2Sharp/BranchUpdater.cs

@@ -154,7 +154,7 @@ private void SetUpstreamRemote(string remoteName)
                 if (!remoteName.Equals(".", StringComparison.Ordinal))
                 {
                     // Verify that remote exists.
-                    repo.Network.Remotes.RemoteForName(remoteName);
+                    using (repo.Network.Remotes.RemoteForName(remoteName)) { }
                 }
 
                 repo.Config.Set(configKey, remoteName);
@@ -183,8 +183,10 @@ private void GetUpstreamInformation(string canonicalName, out string remoteName,
             {
                 remoteName = Proxy.git_branch_remote_name(repo.Handle, canonicalName, true);
 
-                Remote remote = repo.Network.Remotes.RemoteForName(remoteName);
-                mergeBranchName = remote.FetchSpecTransformToSource(canonicalName);
+                using (var remote = repo.Network.Remotes.RemoteForName(remoteName))
+                {
+                    mergeBranchName = remote.FetchSpecTransformToSource(canonicalName);
+                }
             }
             else
             {

LibGit2Sharp/Network.cs

@@ -415,9 +415,12 @@ public virtual void Push(
 
             foreach (var branch in enumeratedBranches)
             {
-                Push(branch.Remote, string.Format(
-                    CultureInfo.InvariantCulture,
-                    "{0}:{1}", branch.CanonicalName, branch.UpstreamBranchCanonicalName), pushOptions);
+                using (var remote = branch.Remote)
+                {
+                    Push(remote, string.Format(
+                        CultureInfo.InvariantCulture,
+                        "{0}:{1}", branch.CanonicalName, branch.UpstreamBranchCanonicalName), pushOptions);
+                }
             }
         }
 
@@ -558,12 +561,16 @@ public virtual MergeResult Pull(Signature merger, PullOptions options)
                 throw new LibGit2SharpException("There is no tracking information for the current branch.");
             }
 
-            if (currentBranch.Remote == null)
+            using (var remote = currentBranch.Remote)
             {
-                throw new LibGit2SharpException("No upstream remote for the current branch.");
+                if (remote == null)
+                {
+                    throw new LibGit2SharpException("No upstream remote for the current branch.");
+                }
+
+                Fetch(remote, options.FetchOptions);
             }
 
-            Fetch(currentBranch.Remote, options.FetchOptions);
             return repository.MergeFetchedRefs(merger, options.MergeOptions);
         }
 

LibGit2Sharp/RepositoryExtensions.cs

@@ -221,8 +221,10 @@ public static void Fetch(this IRepository repository, string remoteName, FetchOp
             Ensure.ArgumentNotNull(repository, "repository");
             Ensure.ArgumentNotNullOrEmptyString(remoteName, "remoteName");
 
-            Remote remote = repository.Network.Remotes.RemoteForName(remoteName, true);
-            repository.Network.Fetch(remote, options);
+            using (var remote = repository.Network.Remotes.RemoteForName(remoteName, true))
+            {
+                repository.Network.Fetch(remote, options);
+            }
         }
 
         /// <summary>