Fix the ordering of month and day.
Fix the ordering of month and day.

I got an INFO message from Bazel containing the following date string:

    "shallow_since": "2018-31-07"

The code seems to reveal that the date is intended to be YYYY-MM-DD, so
change the requested format passed to Git.

Closes #5734.

PiperOrigin-RevId: 207683709

aehlig/bazel,dslomov/bazel-windows,meteorcloudy/bazel,safarmer/bazel,ButterflyNetwork/bazel,safarmer/bazel,dslomov/bazel-windows,katre/bazel,dslomov/bazel-windows,aehlig/bazel,twitter-forks/bazel,bazelbuild/bazel,ButterflyNetwork/bazel,dslomov/bazel,katre/bazel,bazelbuild/bazel,bazelbuild/bazel,safarmer/bazel,bazelbuild/bazel,ulfjack/bazel,davidzchen/bazel,ulfjack/bazel,twitter-forks/bazel,perezd/bazel,twitter-forks/bazel,dslomov/bazel-windows,perezd/bazel,meteorcloudy/bazel,safarmer/bazel,ulfjack/bazel,ulfjack/bazel,werkt/bazel,dslomov/bazel,aehlig/bazel,akira-baruah/bazel,akira-baruah/bazel,meteorcloudy/bazel,werkt/bazel,perezd/bazel,ulfjack/bazel,davidzchen/bazel,aehlig/bazel,dslomov/bazel-windows,werkt/bazel,werkt/bazel,twitter-forks/bazel,katre/bazel,meteorcloudy/bazel,davidzchen/bazel,twitter-forks/bazel,davidzchen/bazel,cushon/bazel,ButterflyNetwork/bazel,meteorcloudy/bazel,cushon/bazel,ulfjack/bazel,aehlig/bazel,akira-baruah/bazel,werkt/bazel,bazelbuild/bazel,perezd/bazel,perezd/bazel,davidzchen/bazel,bazelbuild/bazel,twitter-forks/bazel,akira-baruah/bazel,davidzchen/bazel,dslomov/bazel,twitter-forks/bazel,safarmer/bazel,ButterflyNetwork/bazel,katre/bazel,katre/bazel,dslomov/bazel,meteorcloudy/bazel,werkt/bazel,cushon/bazel,akira-baruah/bazel,ButterflyNetwork/bazel,davidzchen/bazel,aehlig/bazel,perezd/bazel,akira-baruah/bazel,cushon/bazel,aehlig/bazel,dslomov/bazel,cushon/bazel,katre/bazel,dslomov/bazel,dslomov/bazel,ButterflyNetwork/bazel,dslomov/bazel-windows,cushon/bazel,safarmer/bazel,ulfjack/bazel,perezd/bazel,meteorcloudy/bazel