git branch --contains errors "no such commit", while github shows that commit exists -

i want check branches contains github commit.
performed following terminal spells on 1 of boxes running git version 1.9.5.msysgit.1:

git clone git@github.com:npm/npm.git && cd npm git branch -a --contains 5ff786ae103161465d84ecdfdc5b0cfd8839eac8 

surprisingly, i'm getting error such commit not exist @ all:

error: no such commit 5ff786ae103161465d84ecdfdc5b0cfd8839eac8 

how can happen if github shows commit?

as figured out due fact github shows in weired way orphaned commit. performed history rewriting , commit got kicked out of official history. still reachable, if perform

$ git log --all -grep="sort actions dependency order" 

you still find correct commit.