repo: don't look up context for tip node if it's not needed
We were doing repo['tip'].node() or similar in a few places where
repo.changelog.tip() would be enough.
Differential Revision: https://phab.mercurial-scm.org/D4781
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
}