The fix is two-fold:
* Adjust the path for the sed call in devel/libgit2 so that we leave out
openssl from libgit2.pc's Requires.private line, otherwise libgit2-glib will
look for openssl.pc, which does not exist when OpenSSL from base is used.
* Reset libgit2-glib back to 0.26, and import a patch both Arch Linux and
openSUSE have been carrying to fix the build with libgit2 0.27. PORTEPOCH was
not set because there is no libgit2-glib 0.27 and no package could have
possibly been built after r469930.
Approved by: mfechner, gnome (kwm)
Differential Revision: https://reviews.freebsd.org/D15437
303fad494e