SHELL

git diff previous commit

git diff HEAD^ HEAD

diff from last commit

#For instance, to see the difference for a file "main.c" between now 
#and two commits back, here are three equivalent commands:

$ git diff HEAD^^ HEAD main.c
$ git diff HEAD^^..HEAD -- main.c
$ git diff HEAD~2 HEAD -- main.c

git diff previous commit

git diff $commithash^ $commithash