Win32: detect unix socket support at runtime

Windows 10 build 17063 introduced support for unix sockets to Windows.
bb390b1 (git-compat-util: include declaration for unix sockets in
windows, 2021-09-14) introduced a way to build git with unix socket
support on Windows, but you still had to decide at build time which
Windows version the compiled executable was supposed to run on.

We can detect at runtime wether the operating system supports unix
sockets and act accordingly for all supported Windows versions.

This fixes https://github.com/git-for-windows/git/issues/3892

Signed-off-by: Matthias Aßhauer <mha1993@live.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

7 files changed, 50 insertions, 2 deletions

diff --git a/builtin/credential-cache--daemon.c b/builtin/credential-cache--daemon.c
index 3a6a750a8e..17f929dede 100644
--- a/builtin/credential-cache--daemon.c
+++ b/builtin/credential-cache--daemon.c
@@ -294,6 +294,8 @@ int cmd_credential_cache_daemon(int argc, const char **argv, const char *prefix)
 	argc = parse_options(argc, argv, prefix, options, usage, 0);
 	socket_path = argv[0];
 
+	if (!have_unix_sockets())
+		die(_("credential-cache--daemon unavailable; no unix socket support"));
 	if (!socket_path)
 		usage_with_options(usage, options);
 
diff --git a/builtin/credential-cache.c b/builtin/credential-cache.c
index bba96d4ffd..bef120b537 100644
--- a/builtin/credential-cache.c
+++ b/builtin/credential-cache.c
@@ -149,6 +149,9 @@ int cmd_credential_cache(int argc, const char **argv, const char *prefix)
 		usage_with_options(usage, options);
 	op = argv[0];
 
+	if (!have_unix_sockets())
+		die(_("credential-cache unavailable; no unix socket support"));
+
 	if (!socket_path)
 		socket_path = get_socket_path();
 	if (!socket_path)
diff --git a/compat/mingw.c b/compat/mingw.c
index 320fb99a90..4876344b5b 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -3158,3 +3158,22 @@ int uname(struct utsname *buf)
 		  "%u", (v >> 16) & 0x7fff);
 	return 0;
 }
+
+int mingw_have_unix_sockets(void)
+{
+	SC_HANDLE scm, srvc;
+	SERVICE_STATUS_PROCESS status;
+	DWORD bytes;
+	int ret = 0;
+	scm = OpenSCManagerA(NULL, NULL, SC_MANAGER_CONNECT);
+	if (scm) {
+		srvc = OpenServiceA(scm, "afunix", SERVICE_QUERY_STATUS);
+		if (srvc) {
+			if(QueryServiceStatusEx(srvc, SC_STATUS_PROCESS_INFO, (LPBYTE)&status, sizeof(SERVICE_STATUS_PROCESS), &bytes))
+				ret = status.dwCurrentState == SERVICE_RUNNING;
+			CloseServiceHandle(srvc);
+		}
+		CloseServiceHandle(scm);
+	}
+	return ret;
+}
diff --git a/compat/mingw.h b/compat/mingw.h
index 6aec50e412..27b61284f4 100644
--- a/compat/mingw.h
+++ b/compat/mingw.h
@@ -631,3 +631,9 @@ void open_in_gdb(void);
  * Used by Pthread API implementation for Windows
  */
 int err_win_to_posix(DWORD winerr);
+
+#ifndef NO_UNIX_SOCKETS
+int mingw_have_unix_sockets(void);
+#undef have_unix_sockets
+#define have_unix_sockets mingw_have_unix_sockets
+#endif
diff --git a/config.mak.uname b/config.mak.uname
index d0dcca2ec5..fcf3e2d785 100644
--- a/config.mak.uname
+++ b/config.mak.uname
@@ -447,7 +447,6 @@ ifeq ($(uname_S),Windows)
 	NO_POLL = YesPlease
 	NO_SYMLINK_HEAD = YesPlease
 	NO_IPV6 = YesPlease
-	NO_UNIX_SOCKETS = YesPlease
 	NO_SETENV = YesPlease
 	NO_STRCASESTR = YesPlease
 	NO_STRLCPY = YesPlease
@@ -661,7 +660,6 @@ ifeq ($(uname_S),MINGW)
 	NO_LIBGEN_H = YesPlease
 	NO_POLL = YesPlease
 	NO_SYMLINK_HEAD = YesPlease
-	NO_UNIX_SOCKETS = YesPlease
 	NO_SETENV = YesPlease
 	NO_STRCASESTR = YesPlease
 	NO_STRLCPY = YesPlease
diff --git a/git-compat-util.h b/git-compat-util.h
index 7c2a6538e5..044f87454a 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -218,6 +218,18 @@ struct strbuf;
 #define GIT_WINDOWS_NATIVE
 #endif
 
+#if defined(NO_UNIX_SOCKETS) || !defined(GIT_WINDOWS_NATIVE)
+static inline int _have_unix_sockets(void)
+{
+#if defined(NO_UNIX_SOCKETS)
+	return 0;
+#else
+	return 1;
+#endif
+}
+#define have_unix_sockets _have_unix_sockets
+#endif
+
 #include <unistd.h>
 #include <stdio.h>
 #include <sys/stat.h>
diff --git a/t/t0301-credential-cache.sh b/t/t0301-credential-cache.sh
index 8300faadea..f2c146fa2a 100755
--- a/t/t0301-credential-cache.sh
+++ b/t/t0301-credential-cache.sh
@@ -8,6 +8,14 @@ test -z "$NO_UNIX_SOCKETS" || {
 	skip_all='skipping credential-cache tests, unix sockets not available'
 	test_done
 }
+if test_have_prereq MINGW
+then
+	service_running=$(sc query afunix | grep "4  RUNNING")
+	test -z "$service_running" || {
+		skip_all='skipping credential-cache tests, unix sockets not available'
+		test_done
+	}
+fi
 
 uname_s=$(uname -s)
 case $uname_s in