[PATCH 0/3] another series of cg-admin-rewritehist -r fixes

The -r flag is a bit confusing, in that it expects the 1st revision de rewrite, and I caught myself feeding it the last revision not to rewrite instead. Patch #2 catches this early. Although Patch #2 should take care of most problems, a non-zero status returned by a command not-last in a pipe is not caught, even under "set -e", so Patch #1 adds an additional safeguard.

Patch #3 corrects seeding of the rewrite map from -r arguments.