install: retry git fetch on failure

[gromgit]

Since this is the most fragile part of the process for most users, might as well put in additional effort.

Tested with this git shim:

#!/usr/bin/env bash
realgit=/usr/bin/git
if [[ -s ~/.rand_thres ]]; then
  limit=$(<~/.rand_fail)
else
  limit=23456  # around 72%
fi
# See if there's a "fetch" in args
for i in "$@"; do
  if [[ $i == "fetch" ]]; then
    # exit on random
    [[ $RANDOM -le $limit ]] && {
      echo "RANDOM FATAL ERROR" >&2
      exit 1
    }
  fi
done
exec "$realgit" "$@"

[carlocab]

Thanks!

[MikeMcQuaid]

Great idea, thanks @gromgit!