this *actually* works

gistfile1.txt

#!/bin/sh

rev=$GIT_COMMIT

if [ $rev = "1cec7c8c99bc446ccede7141a93a621d0f4e59d0" ]
then
    n="Géraud Continsouzas"; m="geraud@gcu.info";
    export GIT_AUTHOR_NAME="$n"
    export GIT_AUTHOR_EMAIL="$m"
    export GIT_COMMITTER_NAME="$n"
    export GIT_COMMITTER_EMAIL="$m"
fi

if [ $rev = "22840928853892a1b5ed020799702956d2f5ee76" ]
then
    n="Géraud Continsouzas"; m="geraud@gcu.info";
    export GIT_AUTHOR_NAME="$n"
    export GIT_AUTHOR_EMAIL="$m"
    export GIT_COMMITTER_NAME="$n"
    export GIT_COMMITTER_EMAIL="$m"
fi

if [ $rev = "cfb86a338b88a95606ca8361f3c0c2fc6210b384" ]
then
    n="Géraud Continsouzas"; m="geraud@gcu.info";
    export GIT_AUTHOR_NAME="$n"
    export GIT_AUTHOR_EMAIL="$m"
    export GIT_COMMITTER_NAME="$n"
    export GIT_COMMITTER_EMAIL="$m"
fi

if [ $rev = "498de4d5554f9d3e5dba6634e4e7c3c20c5ef28a" ]
then
    n="Géraud Continsouzas"; m="geraud@gcu.info";
    export GIT_AUTHOR_NAME="$n"
    export GIT_AUTHOR_EMAIL="$m"
    export GIT_COMMITTER_NAME="$n"
    export GIT_COMMITTER_EMAIL="$m"
fi