251057d7f3
- enable use of cygwin to build and test s2i - simplify git and file downloaders - track posix file permissions on windows - remove unnecessary runtime.GOOS == "windows" checks - unit test fixes
sigintwrap is an executable wrapper used in the automated testing of s2i on Windows. In hack/test-stirunimage.sh it is verified that sending an interrupt to a running s2i process (i.e. sending a SIGINT on Linux, or specifically pressing CTRL+C or CTRL+BREAK on Windows) causes the process to clean up a running Docker container before exiting.
Cygwin is used for Windows build and testing of s2i, but note that the s2i binary itself has no dependency on Cygwin (in general, Go and the executables it compiles have no knowledge or dependency on Cygwin).
For the above test to be valid and succeed on Windows, it is necessary to bridge between receiving the SIGINT sent by the test framework (note: on Windows, POSIX-style signal handling is implemented only in Cygwin-compiled/-aware executables, in userspace) and Golang acting on a native CTRL+C/CTRL+BREAK event.
sigintwrap is a Cygwin-compiled executable which spawns a named executable in a new Windows process group and waits until it exits. If before that time sigintwrap receives a SIGINT signal it sends a synthetic CTRL+BREAK event to the process it started.
This approach is used (rather than, say, simply using the GenerateConsoleCtrlEvent API directly to create a synthetic event) because there is no obvious and straightforward way to spawn a new process into a new Windows process group in Cygwin without resorting to C, nor is there an obvious free lightweight pre-existing utility which can be used to send a synthetic CTRL+BREAK event to a given process.