git rev-list | grep choke on utf-8 in comments

[ibnHatab]

in Collect revision statistics

lines = getpipeoutput(['git rev-list --pretty=format:"%%at %%ai %%aN <%%aE>" %s' % getlogrange('HEAD'), 'grep -a -v ^commit']).split('\n')
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grep breaks the PIPI with: Binary file (standard input) matches.
Adding -a to grep solves the issue.