Log Message:
(devel/R-git2r) Updated 0.26.1 to 0.27.1

git2r 0.27.1
------------
CHANGES

* Fixed the CITATION file to pass 'R CMD check' without a NOTE.

git2r 0.27.0
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IMPROVEMENTS

* Updated the bundled libgit2 source code to version '0.28.5'.

* Updated the build configuration script to be able to build git2r
  with a system installation of libgit2 version >= 1.0.

* Updated to use libgit2 version 1.0.0 on Windows.

* The build configuration script checks for minimum required version
  of libssh2 (version >= 1.8). Issue #420.

* Updated to use roxygen2 version 7.1.0 to build the documentation.

* Make it easier to view and change the timezone (John Blischak in
  #408).

* Fixed 'ls_tree' to handle content in subfolder, see description in
  PR #402.

* The 'branch_create' function has been changed to use the
  'last_commit()' function as default to determine the commit to which
  the new branch should point.