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-rw-r--r--Documentation/git.txt18
-rw-r--r--compat/mingw.c58
-rwxr-xr-xt/t0001-init.sh12
3 files changed, 88 insertions, 0 deletions
diff --git a/Documentation/git.txt b/Documentation/git.txt
index 7a1d629ca0..463b0eb0f5 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -709,6 +709,24 @@ of clones and fetches.
the background which do not want to cause lock contention with
other operations on the repository. Defaults to `1`.
+`GIT_REDIRECT_STDIN`::
+`GIT_REDIRECT_STDOUT`::
+`GIT_REDIRECT_STDERR`::
+ Windows-only: allow redirecting the standard input/output/error
+ handles to paths specified by the environment variables. This is
+ particularly useful in multi-threaded applications where the
+ canonical way to pass standard handles via `CreateProcess()` is
+ not an option because it would require the handles to be marked
+ inheritable (and consequently *every* spawned process would
+ inherit them, possibly blocking regular Git operations). The
+ primary intended use case is to use named pipes for communication
+ (e.g. `\\.\pipe\my-git-stdin-123`).
++
+Two special values are supported: `off` will simply close the
+corresponding standard handle, and if `GIT_REDIRECT_STDERR` is
+`2>&1`, standard error will be redirected to the same handle as
+standard output.
+
Discussion[[Discussion]]
------------------------
diff --git a/compat/mingw.c b/compat/mingw.c
index 8b6fa0db44..2d44d21aca 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -2139,6 +2139,62 @@ static char *wcstoutfdup_startup(char *buffer, const wchar_t *wcs, size_t len)
return memcpy(malloc_startup(len), buffer, len);
}
+static void maybe_redirect_std_handle(const wchar_t *key, DWORD std_id, int fd,
+ DWORD desired_access, DWORD flags)
+{
+ DWORD create_flag = fd ? OPEN_ALWAYS : OPEN_EXISTING;
+ wchar_t buf[MAX_PATH];
+ DWORD max = ARRAY_SIZE(buf);
+ HANDLE handle;
+ DWORD ret = GetEnvironmentVariableW(key, buf, max);
+
+ if (!ret || ret >= max)
+ return;
+
+ /* make sure this does not leak into child processes */
+ SetEnvironmentVariableW(key, NULL);
+ if (!wcscmp(buf, L"off")) {
+ close(fd);
+ handle = GetStdHandle(std_id);
+ if (handle != INVALID_HANDLE_VALUE)
+ CloseHandle(handle);
+ return;
+ }
+ if (std_id == STD_ERROR_HANDLE && !wcscmp(buf, L"2>&1")) {
+ handle = GetStdHandle(STD_OUTPUT_HANDLE);
+ if (handle == INVALID_HANDLE_VALUE) {
+ close(fd);
+ handle = GetStdHandle(std_id);
+ if (handle != INVALID_HANDLE_VALUE)
+ CloseHandle(handle);
+ } else {
+ int new_fd = _open_osfhandle((intptr_t)handle, O_BINARY);
+ SetStdHandle(std_id, handle);
+ dup2(new_fd, fd);
+ /* do *not* close the new_fd: that would close stdout */
+ }
+ return;
+ }
+ handle = CreateFileW(buf, desired_access, 0, NULL, create_flag,
+ flags, NULL);
+ if (handle != INVALID_HANDLE_VALUE) {
+ int new_fd = _open_osfhandle((intptr_t)handle, O_BINARY);
+ SetStdHandle(std_id, handle);
+ dup2(new_fd, fd);
+ close(new_fd);
+ }
+}
+
+static void maybe_redirect_std_handles(void)
+{
+ maybe_redirect_std_handle(L"GIT_REDIRECT_STDIN", STD_INPUT_HANDLE, 0,
+ GENERIC_READ, FILE_ATTRIBUTE_NORMAL);
+ maybe_redirect_std_handle(L"GIT_REDIRECT_STDOUT", STD_OUTPUT_HANDLE, 1,
+ GENERIC_WRITE, FILE_ATTRIBUTE_NORMAL);
+ maybe_redirect_std_handle(L"GIT_REDIRECT_STDERR", STD_ERROR_HANDLE, 2,
+ GENERIC_WRITE, FILE_FLAG_NO_BUFFERING);
+}
+
void mingw_startup(void)
{
int i, maxlen, argc;
@@ -2146,6 +2202,8 @@ void mingw_startup(void)
wchar_t **wenv, **wargv;
_startupinfo si;
+ maybe_redirect_std_handles();
+
/* get wide char arguments and environment */
si.newmode = 0;
if (__wgetmainargs(&argc, &wargv, &wenv, _CRT_glob, &si) < 0)
diff --git a/t/t0001-init.sh b/t/t0001-init.sh
index 86c1a51654..c413bff9cf 100755
--- a/t/t0001-init.sh
+++ b/t/t0001-init.sh
@@ -453,4 +453,16 @@ test_expect_success 're-init from a linked worktree' '
)
'
+test_expect_success MINGW 'redirect std handles' '
+ GIT_REDIRECT_STDOUT=output.txt git rev-parse --git-dir &&
+ test .git = "$(cat output.txt)" &&
+ test -z "$(GIT_REDIRECT_STDOUT=off git rev-parse --git-dir)" &&
+ test_must_fail env \
+ GIT_REDIRECT_STDOUT=output.txt \
+ GIT_REDIRECT_STDERR="2>&1" \
+ git rev-parse --git-dir --verify refs/invalid &&
+ printf ".git\nfatal: Needed a single revision\n" >expect &&
+ test_cmp expect output.txt
+'
+
test_done