Is there a way in git to count the total deletions and additions for a given user on a given branch? Something like that is on github, in the graph section there is a chart
I don't think Git has any built-in command that does this. But with the help of some other standard utilities, it can be done. Here is an example that filters Git's log output through awk to get the summary of total insertions and deletions:
git log --author=$USER --shortstat $BRANCH | \
awk '/^ [0-9]/ { f += $1; i += $4; d += $6 } \
END { printf("%d files changed, %d insertions(+), %d deletions(-)", f, i, d) }'