tests/test-issue1175

Improvement to 14ce129cfcd: Use try/except and pass filename on errors

Without the second part, the error message would be
  abort: Is a directory
instead of
  abort: Is a directory: /home/user/.cvspass

#!/bin/sh
rm -rf a
hg init a
cd a
touch a
hg ci -Am0
hg mv a a1
hg ci -m1
hg co 0
hg mv a a2
hg up
hg ci -m2

touch a
hg ci -Am3
hg mv a b
hg ci -Am4 a
hg ci --debug --traceback -Am5 b
hg verify
hg export --git tip