[PATCH 1/1] mingw: support spawning programs containing spaces in their names

["Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>]

From: Johannes Schindelin <johannes.schindelin@gmx.de>

On some older Windows versions (e.g. Windows 7), the CreateProcessW()
function does not really support spaces in its first argument,
lpApplicationName. But it supports passing NULL as lpApplicationName,
which makes it figure out the application from the (possibly quoted)
first argument of lpCommandLine.

Let's use that trick (if we are certain that the first argument matches
the executable's path) to support launching programs whose path contains
spaces.

We will abuse the test-fake-ssh.exe helper to verify that this works and
does not regress.

This fixes https://github.com/git-for-windows/git/issues/692

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 compat/mingw.c         | 8 +++++---
 t/t0061-run-command.sh | 6 ++++++
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/compat/mingw.c b/compat/mingw.c
index 9b6d2400e1..6d7fc07a48 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -1437,7 +1437,9 @@ static pid_t mingw_spawnve_fd(const char *cmd, const char **argv, char **deltaen
 	si.hStdOutput = winansi_get_osfhandle(fhout);
 	si.hStdError = winansi_get_osfhandle(fherr);
 
-	if (xutftowcs_path(wcmd, cmd) < 0)
+	if (*argv && !strcmp(cmd, *argv))
+		wcmd[0] = L'\0';
+	else if (xutftowcs_path(wcmd, cmd) < 0)
 		return -1;
 	if (dir && xutftowcs_path(wdir, dir) < 0)
 		return -1;
@@ -1466,8 +1468,8 @@ static pid_t mingw_spawnve_fd(const char *cmd, const char **argv, char **deltaen
 	wenvblk = make_environment_block(deltaenv);
 
 	memset(&pi, 0, sizeof(pi));
-	ret = CreateProcessW(wcmd, wargs, NULL, NULL, TRUE, flags,
-		wenvblk, dir ? wdir : NULL, &si, &pi);
+	ret = CreateProcessW(*wcmd ? wcmd : NULL, wargs, NULL, NULL, TRUE,
+		flags, wenvblk, dir ? wdir : NULL, &si, &pi);
 
 	free(wenvblk);
 	free(wargs);
diff --git a/t/t0061-run-command.sh b/t/t0061-run-command.sh
index ebc49561ac..015fac8b5d 100755
--- a/t/t0061-run-command.sh
+++ b/t/t0061-run-command.sh
@@ -210,4 +210,10 @@ test_expect_success MINGW 'verify curlies are quoted properly' '
 	test_cmp expect actual
 '
 
+test_expect_success MINGW 'can spawn with argv[0] containing spaces' '
+	cp "$GIT_BUILD_DIR/t/helper/test-fake-ssh$X" ./ &&
+	test_must_fail "$PWD/test-fake-ssh$X" 2>err &&
+	grep TRASH_DIRECTORY err
+'
+
 test_done
-- 
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