mingw: help debugging by optionally executing bash with strace
MSYS2's strace facility is very useful for debugging... With this patch, the bash will be executed through strace if the environment variable GIT_STRACE_COMMANDS is set, which comes in real handy when investigating issues in the test suite. Also support passing a path to a log file via GIT_STRACE_COMMANDS to force Git to call strace.exe with the `-o <path>` argument, i.e. to log into a file rather than print the log directly. That comes in handy when the output would otherwise misinterpreted by a calling process as part of Git's output. Note: the values "1", "yes" or "true" are *not* specifying paths, but tell Git to let strace.exe log directly to the console. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>