documentation update: getHeadCommit() returns null if branch does not

exists

Author: host6

README.md

@@ -116,7 +116,7 @@ Note: null passed as a branch name is considered as Master Branch. Any non-null
     - Returns ordered list of `limit` commits (0 is unlimited) starting from commit specified by `firstCommitId` in direction specified by `direction`
     - If `firstCommitId` is null then commits are starting at branch `branchName` first commit (for ASC direction) or at head of branch (for DESC direction)
 - `VCSCommit getHeadCommit(String branchName)`
-    - Returns `VCSCommit` instance pointing to the head (last) commit of the branch `branchName`  
+    - Returns `VCSCommit` instance pointing to the head (last) commit of the branch `branchName` or `null` if the requested branch does not exists  
 - `Boolean fileExists(String branchName, String filePath)`
     - Returns true if the file with path `filePath` exists in repository in branch `branchName`, false otherwise
 - `VCSTag createTag(String branchName, String tagName, String tagMessage) throws EVCSTagExists`