Make reference lookups apply precomposeunicode

Before these changes, looking up a reference would return the
same precomposed or decomposed form of the reference name that
was used to look it up, so on MacOS which ignores the difference
between the two, a single reference could be looked up either way
and git_reference_name would return the form of the name that was
used to look it up!  This change makes lookup always return the
precomposed name if core.precomposeunicode is set regardless of
which version was used to look it up.  The reference iterator was
already returning the precomposed form from earlier work.

This also updates the CMakeLists.txt rules for enabling iconv
usage because the clar tests for this code were actually not being
activated properly with the old version.

Finally, this moves git_repository_reset_filesystem from include/
git2/repository.h to include/git2/sys/repository.h since it is not
really a function that normal library users should have to think
about very often.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/refs.h b/src/refs.h
index 4b91c25e8..80c7703fc 100644
--- a/src/refs.h
+++ b/src/refs.h
@@ -46,6 +46,8 @@
 #define GIT_STASH_FILE "stash"
 #define GIT_REFS_STASH_FILE GIT_REFS_DIR GIT_STASH_FILE
 
+#define GIT_REF_FORMAT__PRECOMPOSE_UNICODE	(1u << 16)
+
 #define GIT_REFNAME_MAX 1024
 
 struct git_reference {