git-wrapper: Allow git-cmd.exe to add only /cmd/ to the PATH

The idea of having the Git wrapper in the /cmd/ directory is to allow
adding only a *tiny* set of executables to the search path, to allow
minimal interference with other software applications. It is quite
likely, for example, that other software applications require their own
version of zlib1.dll and would not be overly happy to find the version
Git for Windows ships.

The /cmd/ directory also gives us the opportunity to let the Git wrapper
handle the `gitk` script. It is a Tcl/Tk script that is not recognized
by Windows, therefore calling `gitk` in `cmd.exe` would not work, even
if we add all of Git for Windows' bin/ directories.

So let's use the /cmd/ directory instead of adding /mingw??/bin/ and
/usr/bin/ to the PATH when launching Git CMD.

The way we implemented Git CMD is to embed the appropriate command line
as string resource into a copy of the Git wrapper. Therefore we extended
that syntax to allow for configuring a minimal search path.

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

Author: dscho

compat/win32/git-wrapper.c

@@ -37,7 +37,7 @@ static void print_error(LPCWSTR prefix, DWORD error_number)
 	LocalFree((HLOCAL)buffer);
 }
 
-static void setup_environment(LPWSTR exepath)
+static void setup_environment(LPWSTR exepath, int full_path)
 {
 	WCHAR msystem[64];
 	LPWSTR path2 = NULL;
@@ -88,19 +88,23 @@ static void setup_environment(LPWSTR exepath)
 	len = sizeof(WCHAR) * (len + 2 * MAX_PATH);
 	path2 = (LPWSTR)malloc(len);
 	wcscpy(path2, exepath);
-	PathAppend(path2, msystem_bin);
-	if (_waccess(path2, 0) != -1) {
-		/* We are in an MSys2-based setup */
-		wcscat(path2, L";");
-		wcscat(path2, exepath);
-		PathAppend(path2, L"usr\\bin;");
-	}
+	if (!full_path)
+		PathAppend(path2, L"cmd;");
 	else {
-		/* Fall back to MSys1 paths */
-		wcscpy(path2, exepath);
-		PathAppend(path2, L"bin;");
-		wcscat(path2, exepath);
-		PathAppend(path2, L"mingw\\bin;");
+		PathAppend(path2, msystem_bin);
+		if (_waccess(path2, 0) != -1) {
+			/* We are in an MSys2-based setup */
+			wcscat(path2, L";");
+			wcscat(path2, exepath);
+			PathAppend(path2, L"usr\\bin;");
+		}
+		else {
+			/* Fall back to MSys1 paths */
+			wcscpy(path2, exepath);
+			PathAppend(path2, L"bin;");
+			wcscat(path2, exepath);
+			PathAppend(path2, L"mingw\\bin;");
+		}
 	}
 	GetEnvironmentVariable(L"PATH", path2 + wcslen(path2),
 				(len / sizeof(WCHAR)) - wcslen(path2));
@@ -163,16 +167,18 @@ static LPWSTR fixup_commandline(LPWSTR exepath, LPWSTR *exep, int *wait,
 
 static int configure_via_resource(LPWSTR basename, LPWSTR exepath, LPWSTR exep,
 	LPWSTR *prefix_args, int *prefix_args_len,
-	int *is_git_command, int *start_in_home, int *skip_arguments)
+	int *is_git_command, int *start_in_home, int *full_path,
+	int *skip_arguments)
 {
-	int id = 0, wargc;
+	int id = 0, minimal_search_path, wargc;
 	LPWSTR *wargv;
 
 #define BUFSIZE 65536
 	static WCHAR buf[BUFSIZE];
 	int len;
 
 	for (id = 0; ; id++) {
+		minimal_search_path = 0;
 		len = LoadString(NULL, id, buf, BUFSIZE);
 
 		if (!len) {
@@ -193,6 +199,12 @@ static int configure_via_resource(LPWSTR basename, LPWSTR exepath, LPWSTR exep,
 			exit(1);
 		}
 
+		if (!wcsncmp(L"MINIMAL_PATH=1 ", buf, 15)) {
+			minimal_search_path = 1;
+			memmove(buf, buf + 15,
+				sizeof(WCHAR) * (wcslen(buf + 15) + 1));
+		}
+
 		buf[len] = L'\0';
 
 		if (!id)
@@ -262,6 +274,8 @@ static int configure_via_resource(LPWSTR basename, LPWSTR exepath, LPWSTR exep,
 		*start_in_home = 0;
 		*skip_arguments = 1;
 	}
+	if (minimal_search_path)
+		*full_path = 0;
 	LocalFree(wargv);
 
 	return 1;
@@ -270,7 +284,8 @@ static int configure_via_resource(LPWSTR basename, LPWSTR exepath, LPWSTR exep,
 int main(void)
 {
 	int r = 1, wait = 1, prefix_args_len = -1, needs_env_setup = 1,
-		is_git_command = 1, start_in_home = 0, skip_arguments = 0;
+		is_git_command = 1, start_in_home = 0, full_path = 1,
+		skip_arguments = 0;
 	WCHAR exepath[MAX_PATH], exe[MAX_PATH];
 	LPWSTR cmd = NULL, dir = NULL, exep = exe, prefix_args = NULL, basename;
 	UINT codepage = 0;
@@ -288,7 +303,8 @@ int main(void)
 	basename = exepath + wcslen(exepath) + 1;
 	if (configure_via_resource(basename, exepath, exep,
 			&prefix_args, &prefix_args_len,
-			&is_git_command, &start_in_home, &skip_arguments)) {
+			&is_git_command, &start_in_home,
+			&full_path, &skip_arguments)) {
 		/* do nothing */
 	}
 	else if (!wcsncmp(basename, L"git-", 4)) {
@@ -346,7 +362,7 @@ int main(void)
 	}
 
 	if (needs_env_setup)
-		setup_environment(exepath);
+		setup_environment(exepath, full_path);
 	cmd = fixup_commandline(exepath, &exep, &wait,
 		prefix_args, prefix_args_len, is_git_command, skip_arguments);