x22 Performance improvement in huge git repository
x22 Performance improvement in huge git repository

The Git.ref() was slow on a git repository which has a huge
'packed-refs' file (e.g. Vim)

This commit improve the peformance of Git.ref() and it made
'gina#component#status#preset()' 22 times faster.

Before (vim/vim)
    Total      Self
    1.110075   0.000126  gina#component#status#preset()
    0.746423   0.000128  gina#component#traffic#preset()
    0.370858   0.021681  gina#component#traffic#ahead()

After (vim/vim)
    Total      Self
    0.053398   0.000208  gina#component#status#preset()
    0.047667   0.000195  gina#component#traffic#preset()
    0.020377   0.001080  gina#component#traffic#ahead()

lambdalisue/gina.vim