fix incorrect warning when walking on a particular rev
when a directory was given instead of a file it reported
incorrectly 'No such file or directory in rev <rev>'
we test if the file is a prefix directory
#!/bin/shhg init aecho a > a/ahg --cwd a ci -A -m ahg clone a becho b > b/bhg --cwd b ci -A -m bchmod 100 a/.hghg --cwd b push ../achmod 700 a/.hg