Update libgit2sharp to v0.18.1
Use the good Signature
Change call to CreateCommit() because used api is obsolete
Fixed according to the discussion

Tested with failing code - compared the result and it matched what is in
TFS
Merge pull request #640 from voloda/Issue#632

#632: Need support for ExtendedMerge of type Delete
Update libgit2sharp to v0.19
Update rcheckin.md
Merge pull request #638 from pmiossec/update_libgit2sharp

Update libgit2sharp to v0.19
Expose a BatchSize option...

Since 21f36fa47c79246afe9a150f3ca46b5afc0190fe, tfs changesets are
 fetched by batches of 100 changesets (instead of all at once)
 to better support big history when cloning (and use less memory).

This option let the user specify the size of the batch
(because perhaps even 100 is too big for some big repositories).

Values accepted:
x < 0 => Only one batch with ALL the changesets
x == 0 => default value of 100
x > 0 => batches of x changesets
Save the option only when cloning
Doc