chg: add fchdirx as a utility function
As part of the series to support long socket paths, we need to use fchdir and
check its result in several places. Make it a utility function.
fixbundle() {
grep -v 'saving bundle' | grep -v 'saved backup' | \
grep -v added | grep -v adding | \
grep -v "unable to find 'e' for patching" | \
grep -v "e: No such file or directory" | \
cat
}