test-merge-tool: Make sure no hgmerge can be found in $PATH
The merge tool selecting algorithm is hardcoded to look for hgmerge in $PATH
before it falls back to use internal merge. This fixes the test for this
fallback to be tolerant to existing hgmerges.
audit: check for casefolding of .hg (
issue1450)
patch: teach selectfile about symlinks (
issue1438)
mq: handle empty patches more gracefully (
issue1501)