cmdutil: replace unix pipe handshake with file lock
The pipe handshake cannot be implemented with Windows detached process, which
disables handle inheritance.
Fix 2/3 for issue421
% wide diffstat
a | 213 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 213 insertions(+), 0 deletions(-)
% diffstat width
a | 213 ++++++++++++++
1 files changed, 213 insertions(+), 0 deletions(-)
% narrow diffstat
a | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)
% binary diffstat
b | 0
1 files changed, 0 insertions(+), 0 deletions(-)
% binary git diffstat
b | Bin
1 files changed, 0 insertions(+), 0 deletions(-)