You can use:
git diff --numstat
to get numerical diff information.
As far as separating modification from an add and remove pair, --word-diff
might help. You could try something like this:
MOD_PATTERN='^.+(\[-|\{\+).*$' \
ADD_PATTERN='^\{\+.*\+\}$' \
REM_PATTERN='^\[-.*-\]$' \
git diff --word-diff --unified=0 | sed -nr \
-e "s/$MOD_PATTERN/modified/p" \
-e "s/$ADD_PATTERN/added/p" \
-e "s/$REM_PATTERN/removed/p" \
| sort | uniq -c
It’s a little long-winded so you may want to parse it in your own script instead.