Describe options structure
Initialize with GIT_DESCRIBE_OPTIONS_INIT macro to correctly set
the version field. E.g.
git_describe_options opts = GIT_DESCRIBE_OPTIONS_INIT;
default: 10
default: GIT_DESCRIBE_DEFAULT
When calculating the distance from the matching tag or reference, only walk down the first-parent ancestry.
If no matching tag or reference is found, the describe operation would normally fail. If this option is set, it will instead fall back to showing the full id of the commit.