git (git-wrapper): use the built-time MSYSTEM value

The idea of the Git wrapper is that it is installed into various places
(as part of the `mingw-w64-git-for-windows-addons` package), e.g. into
`<msys64>\git-bash.exe`. This executable will then set up the required
environment variables and spawn the actual `bash.exe`.

Likewise, the Git wrapper is installed into `<msys64>\cmd\git.exe`
where it can be called directly from, say, a PowerShell, without needing
to add all the correct `PATH` entries and without setting `MSYSTEM`: the
wrapper will do all that, and then spawn the actual `git.exe` in the
correct subdirectory.

Now, grace to Git for Windows' history, which started out before MSYS2
was invented and was based on MSys and MinGW instead, the actual logic
grew organically. In the early days, when Git for Windows only supported
i686 builds, all of those environment variable values were hardcoded.
Later, when Git for Windows was moved on top of MSYS2, only two values
were possible: "MINGW64" and "MINGW32". When timid steps were taken to
support Windows/ARM64, a third option was added: "CLANGARM64".

All this was unnecessary, though: The environment variable `MSYSTEM` is
set when building the mingw-w64-git package, and it is guaranteed to be
set to the very value the Git wrapper wants to use at run-time.

So let's stop hard-coding the MINGW{32,64} values, and drop the hack we
needed in Git for Windows while the clangarm64 builds were only
experimental.

Instead, just use the value in the environment variable `MSYSTEM` at
build time, hard-coding _that_ into the binary. This will allow the Git
wrapper to find the executables that were put into the corresponding
`mingw-w64-git-*` packages.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

mingw-w64-git/PKGBUILD

@@ -61,15 +61,15 @@ sha256sums=('5f624e2511c445b832d9bbd65a74c27630be79994bf38dde4a4f8013d89e60e0'
             'a9dcba5aebc93ae7aacdee03275780fc6c0f15e88fda30c93041e75851e75090'
             '7e6c5f3dc6a4209dca0e1f38880b2978500a5c745c04bc60dbeda5fc48e8d3cb'
             '80b0b11efe5a2f9b4cd92f28c260d0b3aad8b809c34ed95237c59b73e08ade0b'
-            '20613488bbd66bced2ef786448dc335c9cc7a5ef8be800e0d5bab83e36faf584'
+            '26b54e0d45fc172424d941fe7b8b87ec8b5b81f15a71954ca212f4fc9887c8fb'
             'dab3e41e935a33f443a4ff4ef4ce92c191b6d952d9eb37e14885540ad5af99ed'
             'c975292adae1f2666f07f8ee9b7d50576da249d9151c6bd211602adc8d37b6ab'
             '53e630f581bee400100d074189754413afb6670ba1c09a5a3a09c5b575e41e60'
             'db754d6fe6722ad54d43df15ee93b1d9cead406158ed84dcbf35e5b4225469ed'
             'db754d6fe6722ad54d43df15ee93b1d9cead406158ed84dcbf35e5b4225469ed'
             'cbed8b133eb9eec9972f146be5c3ff49db29b2fff8ab9c87a6d0c646c08a5128'
             '027155aa6ca5f11ad7bcb89550a470935a9f22a9d5b3ab80a9eb209983258c1f'
-            '386e965e184f657a5373b117c59e9e8711713e09177623a77718358cbc46296e'
+            'b79173d806af70f211ce7b67684d8f82f5a2661e186eabf831935cf0f360c86d'
             '7413506c59d25621e475aa45447993748332c72cfbb4cf94cce6bee6f1218a09'
             '6d83e1cb1acdb6eb1f2d5cb9299298e57680f5ca43d43c3e67c9da17f21b9b01')
 

mingw-w64-git/git-wrapper.c

@@ -114,48 +114,6 @@ static void my_path_append(LPWSTR list, LPCWSTR path, size_t alloc)
 	}
 }
 
-static int running_on_arm64 = -1;
-
-static int is_running_on_arm64_hardware()
-{
-	if (running_on_arm64 >= 0)
-		return running_on_arm64;
-
-	USHORT process_machine = 0;
-	USHORT native_machine = 0;
-
-	/* Note: IsWow64Process2 is only available in Windows 10 1511+ */
-	BOOL (WINAPI* IsWow64Process2)(HANDLE, PUSHORT, PUSHORT) =
-		(BOOL (WINAPI *)(HANDLE, PUSHORT, PUSHORT))
-		GetProcAddress(GetModuleHandle(L"kernel32"), "IsWow64Process2");
-
-	running_on_arm64 = IsWow64Process2 &&
-		IsWow64Process2(GetCurrentProcess(), &process_machine, &native_machine) &&
-		native_machine == 0xaa64;
-
-	return running_on_arm64;
-}
-
-static int is_running_on_arm64_msystem(LPWSTR top_level_path, LPWSTR msystem_bin)
-{
-	int ret=0;
-	size_t len = wcslen(top_level_path);
-
-	/* Does /clangarm64/bin exist? */
-	my_path_append(top_level_path, L"clangarm64/bin", MAX_PATH);
-	if (_waccess(top_level_path, 0) != -1) {
-		wcscpy(msystem_bin, L"clangarm64/bin");
-		ret=1;
-	}
-	top_level_path[len] = L'\0';
-	return ret;
-}
-
-static inline int is_running_on_arm64(LPWSTR top_level_path, LPWSTR msystem_bin)
-{
-	return is_running_on_arm64_hardware() && is_running_on_arm64_msystem(top_level_path, msystem_bin);
-}
-
 static int is_system32_path(LPWSTR path)
 {
 	WCHAR system32[MAX_PATH];
@@ -165,20 +123,11 @@ static int is_system32_path(LPWSTR path)
 
 static void setup_environment(LPWSTR top_level_path, int full_path)
 {
-	WCHAR msystem[64];
 	LPWSTR path2 = NULL;
 	int len;
 
 	/* Set MSYSTEM */
-	if (running_on_arm64 > 0) {
-		swprintf(msystem, sizeof(msystem),
-				L"CLANGARM64");
-	} else {
-		swprintf(msystem, sizeof(msystem),
-				L"MINGW%d", (int)sizeof(void*) * 8);
-	}
-
-	SetEnvironmentVariable(L"MSYSTEM", msystem);
+	SetEnvironmentVariable(L"MSYSTEM", MSYSTEM);
 
 	/* if not set, set PLINK_PROTOCOL to ssh */
 	if (!GetEnvironmentVariable(L"PLINK_PROTOCOL", NULL, 0))
@@ -633,8 +582,6 @@ static void initialize_top_level_path(LPWSTR top_level_path, LPWSTR exepath,
 	while (strip_count) {
 		if (strip_count < 0) {
 			int len = wcslen(top_level_path);
-			if (is_running_on_arm64(top_level_path, msystem_bin))
-				return;
 			my_path_append(top_level_path, msystem_bin, MAX_PATH);
 			if (_waccess(top_level_path, 0) != -1) {
 				/* We are in an MSys2-based setup */
@@ -665,8 +612,6 @@ static void initialize_top_level_path(LPWSTR top_level_path, LPWSTR exepath,
 		if (strip_count > 0)
 			--strip_count;
 	}
-	/* Only enable ARM64 support if <top-level>/arm64/bin/ exists */
-	is_running_on_arm64(top_level_path, msystem_bin);
 }
 
 static void maybe_read_config(LPWSTR top_level_path)
@@ -720,9 +665,10 @@ int main(void)
 	LPWSTR working_directory = NULL;
 	LPCWSTR prefix_args = NULL;
 
-	/* Determine MSys2-based Git path. */
-	swprintf(msystem_bin, sizeof(msystem_bin),
-		L"mingw%d\\bin", (int) sizeof(void *) * 8);
+	/* Determine MSYS2-based `bin` path. */
+	wcscpy(msystem_bin, MSYSTEM L"\\bin");
+	for (wchar_t *p = msystem_bin; *p; p++)
+		*p = towlower(*p);
 	*top_level_path = L'\0';
 
 	/* get the installation location */

mingw-w64-git/mingw-w64-git.mak

@@ -6,6 +6,7 @@ git-wrapper$(X): git-wrapper.o git.res
 
 git-wrapper.o: %.o: ../%.c GIT-PREFIX
 	$(QUIET_CC)$(CC) $(ALL_CFLAGS) $(COMPAT_CFLAGS) \
+		-DMSYSTEM=L"\"$(MSYSTEM)\"" \
 		-fno-stack-protector -o $*.o -c -Wall -Wwrite-strings $<
 
 git-bash.res git-cmd.res git-wrapper.res gitk.res compat-bash.res tig.res: \